Pseudosarcoma of the skin. An electron microscopic study and comparison with the fine structure of spindle-cell variant of squamous carcinoma

Conception and Management of a Poorly Understood Spectrum of Dermatologic Neoplasms: Atypical Fibroxanthoma, Pleomorphic Dermal Sarcoma, and Undifferentiated Pleomorphic Sarcoma

OPINION STATEMENT

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) tumors share many clinical, etiologic, and histologic features and likely represent components of a tumor spectrum. In dermatologic oncology, differentiating between AFX and PDS is pivotal as tumors with histological features consistent with PDS are more likely to behave in a clinically aggressive manner. Importantly, the term "pleomorphic dermal sarcoma" (PDS) is a more appropriate designation than "undifferentiated pleomorphic sarcoma" (UPS) for describing deeper, more aggressive, histologically high-grade cutaneous tumors that otherwise resemble AFX. Surgery remains the gold standard for treatment. In the setting of AFX, excision with the Mohs micrographic technique appears to offer superior tumor control rates while maintaining greater tissue preservation over wide local excision and should be considered first line. In the setting of PDS, optimal management is less clear given the paucity of available data. However, due to its greater propensity to recur and metastasize, extirpation with complete tumor margin control appears paramount. The roles of imaging and SLNB in management and clinical outcomes of AFX and PDS are unclear given the lack of available data. In reality, these tools are unlikely to be helpful in most cases of AFX. However, in the setting of PDS, emerging literature indicates that these tumors are inherently higher risk, and thus, imaging and SLNB may be helpful in select cases. Additionally, radiation therapy may be of adjuvant benefit for these tumors when clear surgical margins cannot be obtained. While traditional chemotherapy has been largely ineffectual, the recent discovery of key oncogenetic mutations has allowed for the identification of several potential molecular drug targets that may have a therapeutic role with future study. In the unfortunate setting of metastatic disease, a multidisciplinary approach is optimal. Further studies are needed to establish definitive conclusions regarding risk stratification and best management practices.

Cutaneous carcinosarcoma with metastasis to the parotid gland

Cutaneous carcinosarcoma is a rare malignancy that exhibits both mesenchymal and epithelial components. It is similar to nonmelanoma skin cancers in terms of risk and prognostic factors. However, these malignancies are known to have a propensity for local recurrence and metastasis, even with adequate resection margins. Here we report a case of metastatic cutaneous carcinosarcoma to the parotid gland and review the relevant literature.

Immunohistochemical p53 expression patterns in sarcomatoid carcinomas of the upper respiratory tract

Sarcomatoid carcinoma of the upper respiratory tract is a phenotypically complex neoplasm that has triggered much thoughtful discussion regarding histogenic origin and morphologic classification. In particular, its putative epithelial lineage and distinction from a pseudosarcomatous reaction are sometimes questioned. Little is known about the genetic alterations underlying sarcomatoid carcinoma. Although about 45% of conventional squamous cell carcinomas of the upper respiratory tract harbor p53 mutations, the p53 status of sarcomatoid carcinomas is not well established. p53 immunohistochemical analysis using the monoclonal antibody D07 was performed on 23 sarcomatoid carcinomas of the upper respiratory tract. Twenty tumors were biphasic, having dual epithelial and spindled components. In four of these biphasic tumors, the epithelial and spindled components were separately analyzed for p53 gene mutations by sequence analysis. p53 immunohistochemistry was also performed on 19 cases of postradiation stromal atypia. Strong and diffuse p53 staining was detected in 18 (78%) of the 23 sarcomatoid carcinomas. When the spindled component was compared with its corresponding epithelial component, identical patterns of p53 protein expression were noted in 19 (95%) of the 20 biphasic tumors. Weak p53 staining was observed in one (5%) of the 19 cases of postradiation stromal atypia. In the four biphasic tumors evaluated by DNA sequence analysis, p53 status was always the same in the paired epithelial and spindle cell components. These findings help further dispel the notion that sarcomatoid carcinoma represents a reactive spindle cell proliferation (pseudosarcoma) or a collision between a carcinoma and a sarcoma (collision tumor). Instead, the epithelial and spindled components share a common pathway of tumorigenesis despite their conspicuous divergence at the phenotypic level.

Morphological characterization of spindle cell tumors induced in transgenic Tg.AC mouse skin

Transgenic Tg.AC mice carry a v-Ha-ras coding region flanked by a zeta-globin promoter and an SV40 polyadenylation signal sequence. These mice respond to carcinogens by developing epidermal papillomas. In some cases, malignancies develop at the sites of these papillomas. Various patterns of squamous cell differentiation were observed in these malignancies. One malignancy that developed at the site of the papillomas was composed of bundles of spindle cells. This lesion is difficult to distinguish from fibrosarcomas by light microscopy. We characterized 16 of these malignancies (tentatively classified as spindle cell tumors) to determine if they were of epithelial or mesenchymal origin. Papillomas were induced in Tg.AC mice by full thickness wounding, 12-O-tetradecanoyl-13-phorbol acetate treatment, or ultraviolet radiation. With time, some papillomas became broad-based, downwardly invading lesions. These lesions were examined by light microscopy with immunohistochemical analysis for cytokeratins and by electron microscopy. Immunohistochemical examination with a polyclonal anti-cytokeratin antibody demonstrated various degrees of keratin staining in all tumors examined. Attenuated desmosomes were also observed in these lesions by electron microscopy. These results indicate an epithelial origin for these malignancies; therefore, they should be classified as spindle cell carcinomas.

Cutaneous micrographic surgery for atypical fibroxanthoma

BACKGROUND

Atypical fibroxanthoma is a locally aggressive cutaneous tumor of the head and neck. Reported treatments include simple excision, cryosurgery, radiation, and cutaneous micrographic surgery.

OBJECTIVE

We wish to further document the use of cutaneous micrographic surgery for local control of atypical fibroxanthoma.

METHODS

A retrospective study of six cases from the University of Missouri-Columbia and a review of the literature.

RESULTS

Five (84%) of our cases were on the heads of elderly patients with strong evidence of photodamage. Subclinical extension of atypical fibroxanthoma required surgical margins averaging 9 mm. Cutaneous micrographic surgery has been associated with no recurrences.

CONCLUSION

The results of our data demonstrate cutaneous micrographic surgery to be an excellent modality to address this locally aggressive tumor. Cutaneous micrographic surgery is an advantageous therapy for this tumor because of its meticulous tissue removal, tissue mapping, and tissue sparing qualities.

Soft tissue sarcomas in dermatology

BACKGROUND

Dermatofibrosarcoma protuberans, atypical fibroxanthoma, and cutaneous leiomyosarcoma are uncommon soft tissue sarcomas that tend to have a high recurrence rate when removed with standard excisional surgery, and in some cases have been reported to metastasize. These tumors have been reported in the surgical, medical, and pathology literature. The diagnosis and treatment of these tumors is still evolving. Wide excision and surgical techniques involving meticulous surgical margin control appear to be the most efficacious treatment for these problematic tumors.

OBJECTIVE

The surgical, medical, and pathology literature was extensively reviewed to collate the observations of multiple investigators, and to summarize their findings. Literature from medical journals of multiple subspecialties as well as textbooks were reviewed with particular emphasis on diagnosis, histologic features including immunohistochemistry, and useful surgical techniques that facilitate the removal of these difficult tumors.

RESULTS

Dermatofibrosarcoma protuberans is a soft tissue neoplasm of intermediate malignancy that shows a high recurrence rate when treated with standard excision. Wide surgical excision using a 3-cm margin greatly reduces the risk of recurrence, but is not practical in some cases. Evidence is continuing to accumulate that Mohs micrographic surgery may be the treatment of choice for this tumor. Atypical fibroxanthoma is best thought of as a superficial form of malignant fibrous histiocytoma. It is histologically indistinguishable from certain forms of malignant fibrous histiocytoma and differs primarily in its size and superficial location. These tumors are best removed surgically. For most smaller tumors a 1-cm margin, which is carried down to the subcutaneous tissue, provides adequate treatment. In cases where tissue conservation is important, Mohs micrographic surgery has been shown to be very effective. Cutaneous leiomyosarcoma is a rare superficial soft tissue sarcoma that has a high incidence of recurrence after excision and can metastasize. Because of the small number of patients treated, treatment recommendations are still evolving. Currently, wide local excision is recommended with a 3-5 cm margin and removal of the underlying subcutaneous tissue. Mohs micrographic surgery has been used in a small number of cases with good success.

CONCLUSION

Dermatofibrosarcoma protuberans, atypical fibroxanthoma, and cutaneous leiomyosarcoma are soft tissue sarcomas that have a high rate of recurrence when treated with standard surgical techniques and may occasionally metastasize. When removing these tumors it is very important to take adequate margins. Mohs micrographic surgery is proving to be very useful in treating these difficult neoplasms.

Spindle cell neoplasms coexpressing cytokeratin and vimentin (metaplastic squamous cell carcinoma)

Spindle cell squamous carcinoma (SCSC) and atypical fibroxanthoma (AFX) are both spindle cell neoplasms (SCN) that usually arise in areas of solar or ionizing radiation of elderly patients. Both lesions have a similar biologic behavior. In addition, the morphologic and ultrastructural similarities found in AFX and the spindle cell component of SCSC, have led some investigators to conclude that these tumors have a similar cell of origin. We studied 15 SCNs with no evidence of epithelial origin and no morphologic epithelial component, that showed immunohistochemical and ultrastructural evidence that would support metaplastic changes of a squamous cell carcinoma to a neoplasm with mesenchymal characteristics.

Evaluation of spindle cell tumors

The most important aspect of any evaluation of spindle cell tumors in the skin or superficial soft tissues is the clinical examination, as a great deal can be learned from the location, appearance, and size of the tumor in question. As recounted in this chapter, the histologic features of these tumors may also be distinctive; however, in some instances, histologic examination alone is insufficient for diagnosis. In such cases, electron microscopy holds considerable promise, but the technique is too dependent upon both the availability of adequately preserved tissues and access to the technique itself. As a result, immunohistochemistry remains the favored approach to most problematic lesions. In our experience, at least 90% of histologically enigmatic tumors will exhibit a characteristic immunophenotype, the remainder usually being indeterminant for a specific pattern of differentiation. The latter outcome is often the result of improper tissue preservation, but may also reflect the primitive nature of some neoplasms. Fortunately, the least common outcome is an ambiguous or "mixed-lineage" phenotype, in which neither one of two or more patterns of differentiation is resolved with certainty. The most common settings in which these problems arise are the separation of MPNST from LMS, and the recognition of melanocytic lesions as distinct from tumors of peripheral nerve sheath. The latter is clearly of greatest clinical concern, and should be the focus of additional study.

Spindle cell carcinoma of the conjunctiva. An immunohistochemical and ultrastructural study of six cases

Six cases of conjunctival spindle cell carcinoma, a rare variant of squamous cell carcinoma, were studied. The median age of the three men and three women was 63.5 years. The tumors appeared as a single nodule in some patients or diffusely involved the conjunctiva in others. Two of the four individuals with intraocular extension presented with phthisis bulbi. Polyclonal antikeratin antibody was helpful and gave the most consistent results when compared with monoclonal antikeratin antibodies, AE1/3 and PKK1. The electron microscopic study of four lesions also established the epithelial nature of the tumor cells. Intracytoplasmic tonofilaments and a few desmosomes were present. Histopathologically, this variant of squamous cell carcinoma is difficult to distinguish from other spindle cell tumors, and this study demonstrates the value of immunohistochemistry and electron microscopy in supporting the correct diagnosis.

The characterization of squamous cell carcinoma induced by ultraviolet irradiation in hairless mice

Squamous cell carcinomas (SCCs) induced by ultraviolet irradiation in hairless mice were characterized according to their growth, gross appearance and light and transmission electron microscopic features. SCCs arose directly from irradiated skin (ab initio) or progressed from pre-existing epidermal tumours and lesions. SCCs could be graded using guidelines established for human tumours. SCCs comprised 60.8% of the tumours examined. Of these, 35.6% were designated as grade 1, 27.7% as grade 2, 7.9% as grade 3 and 28.7% as grade 4. Spindle cell tumours suspected of being SCCs were included in grade 4. Grades 1, 2 and 3 could not be distinguished on the basis of growth and gross appearance. Those arising ab initio presented as either red, ulcerated lesions or as raised, white, verrucose lesions. Grade 4 SCCs that arose ab initio presented as rapidly growing, red, spherical lesions. Those that arose from pre-existing tumours or lesions had no characteristic appearance, and variable growth. Light microscopically, grade 4 SCCs with an obvious point of origin from epidermis or other epidermal tumours, and putative grade 4 SCCs without such a point of origin, were characterized commonly by spindle cells, pleomorphic giant or multinucleated cells and individual cell reticular fibres. Ultrastructurally, spindle cells, although poorly differentiated, were distinct from flibroblastic proliferations and had few tonofilaments or desmosomes, and were inconsistently surrounded by basal lamina-like material. On the basis of these characteristics, and despite inconclusive positivity with immunoperoxidase staining for keratin and prekeratin, it was concluded that these spindle cell tumours were most probably of identical squamous cell origin.(ABSTRACT TRUNCATED AT 250 WORDS)

"Clear cell" atypical fibroxanthoma

An 87-year-old man with extensive solar damage presented with a 2-month history of a dome-shaped, crusted lesion on the dorsum of the left hand. Microscopically, the tumor consisted of fascicles of spindle cells with bizarre nuclei and clear, vacuolated cytoplasm. Histochemical, immunohistochemical, and ultrastructural features supported the diagnosis of atypical fibroxanthoma. There was no evidence of metastatic disease. The lesion was completely excised, and there has been no recurrence in 3 months of observation. This unusual "clear cell" variant of atypical fibroxanthoma must be distinguished from other clear cell tumors, such as metastatic renal cell carcinoma, clear cell eccrine carcinoma, and clear cell sarcoma (malignant melanoma) of soft parts. Although atypical fibroxanthoma is usually cured by complete surgical excision, metastases have been reported.

Atypical fibroxanthoma of the skin with metastasis

Cutaneous atypical fibroxanthoma (AFX) occurs in elderly persons as a small nodule or ulcernodule in actinically damaged skin of the head and neck area. The vast majority of AFX behave in a benign manner, and metastasis is rare. Eight examples of metastasizing AFX are reported. Factors that portend aggressive behavior and metastasis are vascular invasion, recurrence, deep tissue invasion, tumor necrosis and, possibly, defective or depressed host resistance. The metastasizing primary AFX were located on the head, and the metastasis involved the structures in the region of the parotid gland.

Spindle cell carcinoma (pseudosarcoma) of the anus: a light, electron microscopic and immunocytochemical study of a case

We report a case of polypoid spindle cell squamous carcinoma (pseudosarcoma) occurring in the anal canal. Electron microscopic findings and the demonstration of keratin by an immunoperoxidase method, gave clear cut evidence of the epithelial nature of the sarcomatoid cells forming this tumour. To our knowledge, this is the first reported case in the literature.

Myofibroblasts in fibromatoses. An electron microscopic study

Fifteen cases of fibromatoses were analyzed by electron microscopy, the objective being to compare the incidence and frequency of myofibroblasts in each category. Myofibroblasts were identified in all 15 cases and a considerably large number of these cells appeared in palmar fibromatosis, plantar fibromatosis, and nodular fasciitis. In keloid and cicatricial fibromatosis, however, only a small number of these cells were evident. In seven cases of extra-abdominal desmoid fibromatosis, the frequency of myofibroblasts in the component cells ranged from 10% to 64%, with a mean of 30%. The frequency was high in hypercellular lesions and low in hypocellular lesions, assuming that it would be roughly in parallel to the cellularity of the lesion in extra-abdominal desmoid fibromatosis and in other fibromatoses as well. There appeared to be no particular correlation between the number of myofibroblasts and recurrence of the lesion.

Atypical fibroxanthoma distinguishable from spindle cell carcinoma in sarcoma-like skin lesions. A clinicopathologic and immunohistochemical study of 21 cases

A clinicopathologic study was done of 21 cutaneous, sarcoma-like lesions previously diagnosed as atypical fibroxanthoma, spindle cell carcinoma, or dermal sarcoma. These lesions were most commonly presented as a solitary, often ulcerated nodule, occurring on exposed skin of the face in the elderly or, occasionally, on roentgen-damaged or burnt skin of the head, leg, or hand. Microscopic features of the 21 lesions were, however, not alike, thereby implying that such sarcoma-like lesions had derived from heterogeneous origins. The immunohistochemical staining in a comparative study with two other cases of unequivocal spindle cell squamous carcinoma suggested that these lesions could be histogenetically divided into two different groups: (1) the major group of true atypical fibroxanthoma, consisting of 19 cases, and (2) the minor group of probable spindle cell squamous carcinoma, consisting of 2 cases. Despite a wide histologic spectrum and of heterogeneity of these lesions, there was a benign clinical course in the majority, due in part to the small size and superficial location of the lesions.

Adenoid squamous cell carcinoma of the penis. Report of a surgical case clinically manifested with rapid lung metastasis

A surgical case of an aggressive form of adenoid squamous cell carcinoma of the penis was studied. The histological features of the tumor originating from the coronal region of the penis showed a well differentiated keratinized squamous cell carcinoma in the superficial area, which transformed into, with a zone of transition in between, an alveolar structure in the deep invading portion and in the metastatic tumor in the inguinal lymph nodes. The alveolar lining cells exhibited an undifferentiated appearance with prominent nucleoli, frequent mitotic figures, and vascular invasion. These cells were neither dyskeratotic nor acanthotic as described in the literatures. Mucin was negative in the tumor cells and angiosarcoma was ruled out with a silver impregnation technique. The patient took a rapid downhill course for the ordinary squamous cell carcinoma of the penis, and he expired eight months after penile amputation with a radiological evidence of lung metastasis. These unusual pathological features and an aggressive behavior of this tumor which were not hitherto described for adenoid squamous cell carcinomas necessitated this report. Autopsy was not performed.

Squamous cell carcinoma with sarcoma-like stroma of the female genital tract. Clinicopathologic study of four cases

Four cases of squamous cell carcinoma with sarcoma-like stroma located in the vulva (1), vagina (2) and cervix (1) of postmenopausal women are presented. The gross and microscopic features are very similar to those of similarly named tumors occurring in the upper respiratory and digestive tract and in the skin. Light microscopic, electron microscopic, and immunohistochemical examination provided convincing evidence that these tumors are composed solely of squamous cell carcinoma, which has undergone a spindle cell sarcoma-like transformation in the deeper portions. Follow-up revealed an aggressive clinical course in three of the four patients, who died of their tumor between 2 and 45 months after presentation. At the time of death, two of the patients had widespread metastases and the other had massive local recurrence.

Spindle cell squamous carcinoma: ultrastructural observations

Two spindle cell carcinomas of the skin and one of the breast have been studied by electron microscopy. In one tumour the spindle cells were of purely mesenchymal type and in the other two the spindle cells exhibited both mesenchymal and epithelial features within the same cells. The significance of the findings in relation to the histogenesis of the spindle cells is discussed, with special reference to the possible alternative roles of mesenchymal metaplasia of the epithelial component and spontaneous cell fusion between carcinoma cells and stromal cells.

Aggressive fibromatosis involving the paramandibular soft tissues. A study with the aid of electron microscopy

The distinction at the level of light microscopy between aggressive fibromatosis and low-grade malignancies with fibroblastic features may be difficult. An electron microscopic study of four cases of aggressive fibromatosis of the mandibular soft tissue was undertaken to determine whether any ultrastructural characteristics could be identified that would aid in a more uniform distinction between these lesions. The pertinent findings include the identification of cells of fibroblastic derivation showing a range of organelle-poor to organelle-rich features, cytoplasmic microfibrils, and dilated rough endoplasmic reticulum profiles. These features are discussed in the light of previously published findings of other forms of aggressive fibromatosis and closely related lesions. The study reaffirms that although electron microscopy may be useful in confirming the cell of origin in these lesions, the accurate diagnosis of fibrous tumors still rests with the proper correlation of clinical and light microscopic features. Clinical follow-up of the cases supports both the diagnosis of aggressive fibromatosis and the recommended treatment of adequate local excision.

Differential diagnosis of spindle cell tumours by electron microscopy--personal experience and a review

Electron microscopy has its value and its limitations in refining the histogenetic diagnosis of certain spindle cell tumours. The ultrastructural diagnostic features of neural tumours, muscle tumours, fibrous histiocytomas, fibrosarcomas, monophasic synovial sarcoma and spindle-cell squamous carcinoma are reviewed and illustrated.

Spindle cell carcinoma of the glans penis: a light and electron microscopic study

Spindle cell carcinoma of the penis has been documented by light microscopy only once in the past. This case report illustrates the light and electron microscopy of a second case. Contrary to previously expressed opinions, polypoid spindle cell carcinomas are not necessarily associated with a good prognosis.

The ultrastructure of a keloid

An active, symptomatic keloid from a 57-year-old woman was examined by both light and electron microscopy. The lesion was found to be comprised entirely of myofibroblasts. Fibroblasts in keloids can apparently undergo full transition to this smooth muscle-like cell.

Proliferating pilar cyst with spindle cell component

Proliferating pilar cysts are rare tumors which occur most commonly on the scalp of elderly women. The infiltrative areas of these tumors should be differentiated from epidermoid carcinoma because they are usually benign. The intimate association of this entity with a spindle cell component is described here, to our knowledge for the first time.

Pseudosarcomatous carcinoma of the esophagus--reference to its histogenesis

A case of pseudosarcomatous carcinoma of the esophagus with metastasis to lymph node was presented and the literature was reviewed briefly. Transition from carcinomatous to sarcomatous picture was noted and the presence of tonofibrils and desmosomes was demonstrated by electron microscope in the cells with sarcomatous features. These findings suggested an epithelial origin of the sarcomatous component in pseudosarcomatous carcinoma.

Fine structural studies of radiation-resistant human squamous cell carcinomas

Squamous cell carcinomas of the oral cavity are relatively common lesions, and often can be controlled by radiation therapy. Recently, a series of these tumors has been encountered which did not respond positively to irradiation, necessitating subsequent extensive surgery. This report describes some fine structural changes which were observed in squamous cell carcinomas following exposure to x-irradiation. In addition to the common, keratin-forming differentiated cell, others which were observed were secretory-like, undifferentiated and phagocytic cells. Undifferentiated tumor cells occasionally became incorporated, at least temporarily, as a component of the blood vessel wall, perhaps reflecting metastatic potentiality. It is proposed that irradiation may either increase potential avenues of tumor cell differentiation or inactivate inhibitors thereof.

Atypical fibroxanthoma of the skin: an ultrastructural study of two cases

The ultrastructure of two atypical" fibroxanthomas of the skin was studied. The first lesion was a spindle cell tumor on light microscopy, which electron microscopy revealed was composed of undifferentiated mesenchymal cells. The second lesion had a highly pheomorphic appearance on both light and electron microscopy. It was formed by atypical histiocytic cells and abundant "typical" Langerhans cells. The second lesion was considered to be a proliferation either of atypical Langerhans cells or of histiocytes related to Langerhans cells. Thus, atypical fibroxanthoma of skin may not be a homogeneous entity but could be a group of mesenchymal proliferative lesion in a similar clinical setting.

Ultrastructure of atypical fibroxanthoma

Electron microscopic examination of an atypical fibroxanthoma (AFX) confirmed the fibrohistiocytic nature of this lesion. Ultrastructural evidence suggested a transition from fibroblasts to large giant cells with intermediate forms exhibiting features of both. A comparison of AFX ultrastructural features to those of other similar neoplasms suggested a possible relationship to malignant fibrous histiocytoma. As diagnosed by light microscopy, AFX probably represents a spectrum of neoplasms; this concept is discussed. It is urged, when possible, that electron microscopy be performed on lesions diagnosed as atypical fibroxanthoma since ultrastructure studies represent the most valid basis on which a correct diagnosis can be made.

Atypical fibroxanthoma of the skin. Presentation of 5 cases and a review of the literature

A typical fibroxanthoma is a solitary tumour of the skin, which occurs mostly on sun-exposed areas in elderly people. The diagnosis can only be made with certainty on the typical histological findings, which suggest a bizarre malignant tumour. Although metastasizing tumours are reported in the literature, the authors believe that the true atypical fibroxanthoma is benign. Correct diagnosis obviates the need for unnecessary radical surgery. The possibility of atypical fibroxanthoma should always be considered when a histologically bizarre tumour is found on sun-damaged or irradiation-damaged skin in elderly patients or on previously traumatized sites. In this paper five cases are added to the 346 cases culled from the literature. Electron microscopic investigations in one case demonstrated cells with delicate cytoplasmic fibrils in small bundles. This does not necessarily suggest filaments of myofibroblasts, as has been previously reported.

Ultrastructure of sclerotic cemental masses

Electron microscopic findings in a focus of early calcification in a case of sclerotic cemental masses of the jaws are described. The lesional cells generally resemble typical collagen-producing cells, except that many contain unusually large numbers of intracytoplasmic actinlike filaments. This and other fine structural features are reminiscent of fibroblasts involved in active tissue repair. These observations suggest that the lesion is basically reactive in its biologic nature. The most characteristic portion of the mineralized component, the rounded calcified globules, ultrastructurally resembles primary cementum.

Spindle cell carcinoma: ultrastructural evidence of squamous origin and collagen production by the tumor cells

Two cases of spindle cell carcinoma (SCC) of the esophagus and skin, respectively, were studied by transmission electron microscopy. The tumor cells were closely associated with collagen fibrils and had abundant rough endoplasmic reticulum with dilated cisternae. Except for their irregular shape and atypical nuclei they resembled actively synthesizing fibroblasts. In addition to these features, some cells contained numerous tonofibrils and occasional well-developed desmosomes. A gradual transition to typical squamous cells was noted in the skin tumor. These findings suggest that the pseudosarcomatous component of SCC originates from mesenchymal metaplasia of squamous cells and that collagen is produced by these metaplastic cells.

Ultrastructure of spindle cell squamous carcinoma

A 63-year-old white male presented with a nine-month history of a nontender ulcerated lesion on his ear. Light microscopy demonstrated a moderately well circumscribed lesion in the dermis which abutted upon epidermis. There was no evidence of continuity between the tumor and overlying epithelium. The tumor was very cellular with an admixture of cells - spindle, polyhedral and bizarre giant cells. Mitotoc figures were abundant and frequently abnormal. We interpreted this lesion to have the clinical and pathologic features of an atypical fibroxanthoma (AFX). Ultrastructure, however, showed abundant tonofilaments and desmosomes indicative of an epithelial origin and therefore most consistent with a spindle cell squamous carcinoma (SCSC). It is urged that, when possible, electron microscopy be performed on problematic cases diagnosed either as an AFX or spindle cell squamous carcinoma since it is the most valid basis on which a correct diagnosis can be made.

Microfilaments in human epithelial cancer cells

The occurence, distribution, and ultrastructural morphology of microfilaments in malignant epithelial cells of invasive squamous cell carcinoma of human oral cavity were studied by electron microscopy. The findings are compared with those in malignant oral epithelial cells of carcinoma-in-situ. In the malignant cells of invasive carcinoma, microfilaments 50-70 A in diameter are prominent in the cortical cytoplasm of the lateral and basal cell surfaces, adjacent and parallel to the plasma membrane, and extending into cell processes and microvillous extensions. Additional microfilaments are found to run from the peripheral cytoplasm to the perinuclear region. The microfilaments are aggregated into bundles aligned parallel to the long axis of the cell and display foci of increased electron density. They also tend to be aggregated into complex polygonal arrays. These microfilaments are similar in organization, concentration and ultrastructural architecture to those of various other nonmuscle cells, where they are thought to be capable of contraction and associated with cell motility. The presence of a microfilament system believed to be associated with contractile and motile cell processes may be an important characteristic of malignant cells of invasive tumors. The lack of abundant organized microfilaments in malignant cells in the absence of tumor invasion, and the presence of a prominent microfilament system in cells of invasive tumors, suggest that the microfilaments are related to the invasive properties of malignant tumor cells.