Single-cell transcriptomic analysis of endometriosis

Endometriosis is a common condition in women that causes chronic pain and infertility and is associated with an elevated risk of ovarian cancer. We profiled transcriptomes of >370,000 individual cells from endometriomas (n = 8), endometriosis (n = 28), eutopic endometrium (n = 10), unaffected ovary (n = 4) and endometriosis-free peritoneum (n = 4), generating a cellular atlas of endometrial-type epithelial cells, stromal cells and microenvironmental cell populations across tissue sites. Cellular and molecular signatures of endometrial-type epithelium and stroma differed across tissue types, suggesting a role for cellular restructuring and transcriptional reprogramming in the disease. Epithelium, stroma and proximal mesothelial cells of endometriomas showed dysregulation of pro-inflammatory pathways and upregulation of complement proteins. Somatic ARID1A mutation in epithelial cells was associated with upregulation of pro-angiogenic and pro-lymphangiogenic factors and remodeling of the endothelial cell compartment, with enrichment of lymphatic endothelial cells. Finally, signatures of ciliated epithelial cells were enriched in ovarian cancers, reinforcing epidemiologic associations between these two diseases.

Myofibroblastic stromal hyperplasia of the breast

Myofibroblastic stromal hyperplasia (MSH) is the proposed name for a benign spindle cell proliferation of the mammary stroma, which often raises clinical and radiographic concern for a mass or a malignant process. Ten cases were retrieved from the files of our institution. All presented as a mammographic abnormality. Patients ranged in age from 24 to 67 years. Seven were <50 years old. The salient histopathologic aspect was the proliferation of benign appearing spindle cell within the intralobular stroma. The most common pattern was a diffuse proliferation of compact spindle cells with areas of perilobular/periductal accentuation. Mitotic activity and atypia were not seen. Tumor cells were positive for CD34 and SMA and negative for estrogen receptor, Beta-catenin, and p63. Only one of the cases demonstrated an associated lesion that explained the mammographic abnormality. Follow-up was available for four cases and was uneventful. MSH has overlapping features with the fascicular pattern of PASH and is likely related to pseudoangiomatous stromal hyperplasia (PASH) but differs in that does not demonstrate pseudovascular structures and it predominantly involves perilobular stroma. Recognition of this pattern will avoid discordant radiologic pathologic findings and unnecessary surgery/repeat biopsies.

Clinicopathologic and molecular features of six cases of phosphaturic mesenchymal tumor

Phosphaturic mesenchymal tumors (PMT) are rare neoplasms characterized by secretion of FGF23, resulting in renal phosphate wasting and osteomalacia. This tumor-induced osteomalacia (TIO) is cured by complete resection; thus, diagnosis is important, particularly on biopsy. Although PMT have a classic histologic appearance of bland spindled cells with conspicuous vascular network and characteristic smudgy basophilic matrix, there is a broad histologic spectrum and variant histologic patterns can make recognition difficult. Recent studies have demonstrated FN1-FGFR1 and FN1-FGF1 gene fusions in PMT; however, approximately 50% of cases are negative for these fusions. We sought to characterize 6 cases of PMT in-depth, compare fusion detection methods, and determine whether alternative fusions could be uncovered by targeted RNA sequencing. Of the 6 cases of PMT in our institutional archive, 3 were not given diagnoses of PMT at the time of initial pathologic examination. We characterized the immunoprofile (SMA, D2-40, CD56, S100 protein, desmin, SATB2, and ERG) and gene fusion status (FN1 and FGFR1 rearrangements by fluorescent in situ hybridization (FISH) and two targeted RNA sequencing approaches) in these cases. Tumors were consistently positive for SATB2 and negative for desmin, with 5/6 cases expressing ERG and CD56. One specimen was acid-decalcified and failed FISH and RNA sequencing. We found FN1 gene rearrangements by FISH in 2/5 cases, and a FN1-FGFR1 fusion by targeted RNA sequencing. No alternative gene fusions were identified by RNA sequencing. Our findings suggest that IHC and molecular analysis can aid in the diagnosis of PMT, guiding excision of the tumor and resolution of osteomalacia.

Histopathologic, immunophenotypic, and proteomics characteristics of low-grade phyllodes tumor and fibroadenoma: more similarities than differences

Distinguishing low-grade phyllodes tumor from fibroadenoma is practically challenging due to their overlapping histologic features. However, the final interpretation is essential to surgeons, who base their management on the final pathology report. Patients who receive a diagnosis of fibroadenoma might not undergo any additional intervention while lumpectomy with wide margins is the standard of care for phyllodes tumor, which can have significant cosmetic consequences. We studied the clinical, immunophenotypic, and proteomics profiles of 31 histologically confirmed low-grade phyllodes tumor and 30 fibroadenomas. Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) and immunohistochemistry for Ki-67, p53, β-catenin, and E-cadherin were performed on all cases. After the mass spectra for all 31 cases of low-grade phyllodes tumor and 30 cases of fibroadenoma were collected, an average peak value for all cases was generated. There was no significant difference in the overall mass spectra pattern in any of the peaks identified. There was also overlap in the percentage of cells staining positive for Ki-67, p53, β-catenin, and E-cadherin. The two groups of patients showed no statistically significant difference in age, tumor size, or disease-free survival. Neither group developed malignant transformation, distant metastases, or disease-related mortality. We have demonstrated low-grade phyllodes tumor and fibroadenoma to show significant overlapping clinical and proteomics features.

Clinicopathologic characteristics of de novo nodular regenerative hyperplasia in pediatric liver transplant

Liver NRH is seen in all patients age; however, more frequently in those over the age of 60 years and associated with multiple systemic diseases. In liver allograft recipients, the development of DnNRH has been linked with the use of azathioprine or vascular abnormalities. We present the clinicopathologic characteristics of 17 pediatric patients who underwent liver transplantation and subsequently developed DnNRH. The patients were divided into early and late onset depending if DnNRH was diagnosed within or beyond 4 years after transplant. Eight patients (47%) presented as early onset, of which two had normal ultrasound at time of diagnosis. One patient (12.5%) with early onset lost the graft secondary to DnNRH. Nine patients (53%) presented as late onset, of which two (22%) had normal ultrasound at time of diagnosis. Two patients (25%) of the late onset lost their graft secondary to chronic rejection and DnNRH. Two patients (12%) died secondary to cytomegalovirus pneumonitis and pancolitis. Furthermore, both groups presented with symptoms differing from the adult population in prior studies and were not associated with the use of azathioprine or vascular abnormalities. Interestingly, episodes of acute cellular rejection were more common in the early-onset group compared to the late-onset group. In conclusion, DnNRH in the pediatric age group has a different clinical presentation, possibly reflecting a different pathogenesis compared to the adult population.

Pediatric Sloughing Esophagitis: A Case Report and Discussion

BACKGROUND

Sloughing esophagitis is an uncommon entity with an unclear pathogenesis characterized by desquamating sheets of squamous mucosa. It has been associated with bullous dermatologic disorders, other autoimmune diseases and has been most commonly reported in elderly, debilitated individuals on multiple medications.

CASE REPORT

We report sloughing esophagitis in a previously healthy 17 year-old girl. While the initial trigger of her esophagitis is unclear, she improved with proton pump inhibitor therapy and swallowed fluticasone, with complete resolution after 6 months.

CONCLUSIONS

Sloughing esophagitis can occur in the pediatric population. We discuss the presentation, differential diagnosis, and treatment of sloughing esophagitis in adolescents.

Acute graft-versus-host disease is more prevalent and severe in the lower than the upper gastrointestinal tract

It is unclear whether acute gastrointestinal (GI) graft-versus-host disease (GVHD) affects all segments of the GI tract equally. Up to 45% patients reported showed discrepancy in involvement between upper GI (UGI) and lower GI (LGI) tract. We compared the prevalence and the severity of acute GVHD in UGI and LGI tract on histologic examination. A cohort of 110 cases of simultaneous UGI and LGI biopsies from 105 allogeneic hematopoietic stem cell transplantation recipients with clinically confirmed GI GVHD were reviewed retrospectively. The χ(2) test and 1-way analysis of variance test were used for statistical analysis. Most (75%) of the cases had GVHD involvement in both UGI and LGI tracts, whereas UGI-only GVHD was found in 6% and LGI-only GVHD in 19%. GVHD prevalence was the lowest in stomach (61%) and significantly increased toward duodenum/jejunum (81%; P = .0019). The LGI tract showed similar GVHD prevalence (P = .3648); the highest was in the sigmoid colon (97%). The histologic grade was lowest in the stomach (mean ± SD, 1.6 ± 0.8) and was similar across all UGI segments (P = .0883). The histologic grade in LGI significantly increased (P = .0265) from the terminal ileum (2.0 ± 1.3) to the rectum (2.9 ± 1.0). Overall, both the prevalence and the histologic grade of GVHD in LGI were significantly higher than those of UGI (P < .0001 for both). Our results show that acute GVHD had a higher prevalence and was more severe in the LGI than in UGI tract. A small subset of patients had only UGI involvement.

Peridiverticular colonic hyaline rings (pulse granulomas): Report of two cases associated with perforated diverticula

Hyaline ring (pulse granuloma) is a rare benign lesion of the oral cavity soft tissues characterized by round or oval structures with scalloped borders composed by a collagenous matrix variable associated with inflammatory and foreign bogy giant cells. Vegetable fragments are variably identified. Whereas most cases occur in the oral cavity, it has also been described in other sites such as the lung and rectum. It is thought by most to represent a reaction to foreign materials. We report two incidentally discovered cases of colonic hyaline rings associated with perforated diverticulitis. Vegetable residues were seen in both cases.

Spindle cell ossifying amyloidotic tumor of the fallopian tube

We report a unique tumor of the fallopian tube that was an incidental finding in a 60-year-old woman. The tumor was characterized by nests of spindle cells embedded in a partially ossified, hyalinized stroma, that also contained amyloid and basement membrane-like material. The histologic appearance of the tumor cells suggested an epithelial nature, but no immunohistochemical or ultrastructural evidence of such was found. The circumscription of the tumor and its lack of mitotic activity and cytologic atypia suggest a benign nature, but the histogenesis and appropriate classification of the tumor remain unclear.

Differential diagnosis of solid carcinoma in situ

Although most cases of carcinoma in-situ are easily classified as either ductal or lobular on the basis of their pattern of involvement and the nature of their cell-to-cell relation, a few pose diagnostic problems. Attention to the presence of associated lesions and the results of immunohistochemical staining for E-cadherin and, to a lesser extent, cytokeratin can help to categorize problematic cases. This article reviews the histological criteria employed to separate ductal carcinoma in situ from lobular carcinoma in situ, the role of immunohistochemistry in the diagnosis of equivocal lesions, and the evidence suggesting the existence of combined and truly hybrid forms.

Endoscopic bile duct brushing of malignant pancreatic biliary strictures: retrospective study with comparison of conventional smear and ThinPrep techniques

Endoscopic bile duct brushing (EBDB) is carried out to differentiate benign from malignant biliary strictures in patients who have pancreaticobiliary disease. The sensitivity of this method for the diagnosis of malignancy is relatively low. The aim of this study is to analyze the cytomorphologic features that are helpful in increasing the sensitivity of detecting these lesions on cytologic samples. These features are compared with slides prepared with the ThinPrep technique. The study included 142 patients with bile duct obstruction or pancreatic mass who underwent EBDB and follow-up surgery or biopsy between 1997 to 2000. Twenty-five (18%) of these cases were positive for malignancy in both EBDB and follow-up surgical biopsy; 20 of these cases were used as positive controls (PC). Sixty-one (43%) were negative in both EBDB and follow-up surgical biopsy specimens, and 21 of those cases were used as negative controls (NC). Fifty-six (39%) cases were negative/atypical in EBDB cytology but were suspicious or positive in the surgical or biopsy specimens (false-negative). We identified the cytologic criteria that were helpful in differentiating our positive and negative control groups and applied these criteria to our false-negative group to see whether our sensitivity could be increased, using well-defined cytologic criteria alone. Of the 56 false-negative cases, 9 (16%) were upgraded to suspicious/positive based on the presence of the following features: three-dimensional (3D) micropapillae (95% PC vs 19% NC, P < 0.0001), anisonucleosis (90% PC vs 5% NC, P < 0.0001), high nuclear-to-cytoplasmic (N/C) ratio (95% PC vs 9% NC, P < 0.0001), nuclear contour irregularity (65% PC vs 24% NC, P = 0.0079), and prominent nucleoli (70% PC vs 38% NC, P = 0.0406). Cytomorphologic features which were not helpful in distinguishing positive and negative cases were: single naked nuclei (50% PC vs 28% NC, P = 0.1597), chromatin granularity (50% PC vs 62% NC, P = 0.54), and necrosis (10% PC vs 5% NC, P = 0.5197). Improvement in diagnostic sensitivity for carcinoma of pancreaticobiliary tract in EBDB samples may be achieved by identifying the key malignant cytomorphologic features: 3D micropapillae, anisonucleosis, nuclear contour irregularity, prominent nucleoli, and high N/C ratio. The sensitivity in detecting malignant biliary strictures increased from 31% to 42% based on these criteria in our current study.

Glomus tumor of the ovary: report of a case with immunohistochemical and ultrastructural observations

A 54-year-old woman was found to have a right adnexal mass during routine pelvic examination. A total abdominal hysterectomy and salpingo-oophorectomy were performed. A well circumscribed, 2.5 cm right ovarian was composed of small spindle and epithelioid cells in solid perivascular nests. The tumor cells were reactive for vimentin and smooth muscle actin. Ultrastructurally, pinocytotic vesicles and basement membrane were prominent. This is the second reported case of glomus tumor of the ovary and the third occurring in the gonads.

Solid low-grade in situ carcinoma of the breast: role of associated lesions and E-cadherin in differential diagnosis

Low-grade solid in situ carcinomas of the breast are difficult to classify. The authors investigated 12 cases of in situ carcinomas with equivocal features and correlated their histologic attributes with those of the associated invasive carcinomas as well as with E-cadherin expression in both in situ and invasive disease. E-cadherin-positive in situ lesions were invariably associated with invasive carcinomas of the ductal type. In situ carcinomas that were E-cadherin negative were associated with invasive carcinomas of the lobular type in five of six cases. In all cases, the invasive carcinomas showed the same pattern of E-cadherin reactivity as the in situ lesions. Sharply defined cellular membranes, necrosis, and occasional microacini were seen in both E-cadherin-positive and negative in situ carcinomas, whereas intracytoplasmic lumina and a noncohesive appearance were seen only in E-cadherin-negative lesions.

Immunohistochemical characterization of pleomorphic giant cells in basal cell carcinoma

Over 20 cases of basal cell carcinomas with pleomorphic giant cells of the mononuclear or multinucleate type have been described. The nature of these cellular and nuclear changes has not been elucidated. Some authors found that these cells have phagocytic properties and others reported an aneuploid DNA content. We have seen mitotic figures in some of these giant cells, and postulate that these cells are capable of proliferation. Twelve cases of basal cell carcinoma with pleomorphic giant cells were examined using monoclonal antibodies recognizing the proliferating cell nuclear antigen (PCNA), Ki-67, and bcl-2 antigens. Expression of proliferation associated antigens in the giant cell population was higher than in the small cell population. Over expression of bcl-2 was detected in both the small and giant cells in all cases. The results demonstrate that the giant tumor cells are cycling and express bcl-2 protein in a manner consistent with basal cell carcinoma. The changes are unlikely to represent a senescent change as seen occasionally in mesenchymal neoplasms.

Collagenous spherulosis: an ultrastructural study

Ultrastructural findings are described in two cases of collagenous spherulosis associated with intraductal hyperplasia and sclerosing adenosis. The spherules showed a variable composition of basement membrane, banded collagen, and mineral deposition. Some spherules were connected to the periacinal stroma by a thin pedicle. The authors propose that spherules represent a peculiar form of stromal invagination that could be seen in a variety of breast lesions, rather than a form of intraductal hyperplasia.

Endocrine mucin-producing sweat gland carcinoma: a cutaneous neoplasm analogous to solid papillary carcinoma of breast

We describe two cases of a distinctive in situ and invasive cutaneous adnexal neoplasm occurring in the eyelid. Mucinous carcinoma represented the invasive portion of the tumor in one case, whereas the other infiltrated in small solid nests. The in situ component is identical to the recently described solid papillary carcinoma of the breast (endocrine ductal carcinoma in situ). Both tumors produced intra- and extracellular mucin, exhibited endocrine differentiation by immunohistochemistry and ultrastructural analysis, and were positive for estrogen and progesterone receptors.

Metaplastic carcinoma of the breast with melanocytic differentiation

We report the clinical and pathologic findings of a metaplastic carcinoma of the breast that exhibited melanocytic differentiation. The tumor possessed both in situ and invasive components. Lower grade regions of the infiltrating carcinoma had features of tubular, mucinous, and matrix-producing carcinomas. In the higher grade areas, conventional poorly differentiated ductal carcinoma merged with an anaplastic neoplasm that looked like malignant melanoma. The nonpigmented cells stained for keratin but lacked HMB-45 and S-100 proteins, whereas the cells containing melanin showed the opposite characteristics. Electron microscopic examination disclosed melanosomes in the neoplastic cells. We believe that these observations convincingly establish both the origin of the tumor from the mammary epithelium and the synthesis of melanin by the tumor cells. We propose the diagnosis of metaplastic carcinoma with melanocytic differentiation for this neoplasm and suggest that the phenomenon of melanocytic metaplasia might underlie the formation of primary melanomas of the breast.

Solid papillary carcinoma of breast: an ultrastructural study

Solid papillary carcinoma of the breast is a subset of papillary carcinoma, which occurs in older women and usually has a favorable prognosis. It is primarily intraductal but also is often associated with invasive carcinoma, especially mucinous carcinoma. Intracellular and extracellular mucin is also found in the in situ stage, in most tumors. In addition to forming solid papillary masses, the cells palisade around vessels in pseudorosettes and show minimal nuclear atypia. Some cells show neuroendocrine differentiation, based on argyophilia with Grimelius staining. Four examples of this neoplasm were studied electron microscopically. Myoepithelial cells were not found. Neoplastic cells had an ultrastructure that was generally similar to that of other types of mammary carcinoma. There were extracellular microlumens, but intracellular lumens and pseudolumens were few or absent. Secretory activity varied among cells, and those cells appearing active had a variety of granule types, including typical flocculent and "bull's-eye" mucinous granules, small dense-core granules, and large serous-like granules. Some of the dense-core granules were interpreted as neuroendocrine in nature, based on their abluminal or juxtavascular location, whereas others that were apical and subluminal were probably mucinous in type. The large serous-appearing granules were subluminal in some cells and diffuse in others and may also have represented a variant of mucinous granules. The results support earlier opinions that accurate interpretation of specific granular function at the electron microscopic level depends on cytochemical studies using uranaffin as a marker of neuroendocrine activity. Although mucinous granules are identified by their lack of staining with uranaffin, the nature of the serous-appearing granules would still not be answered by this method; that is, a negative reaction would not define whether the granules are truly serous, or simply another form of mucin. Regardless of limitations of this type, correlation and extrapolation of histochemical (Grimelius and Alcian blue) and immunohistochemical (chromogranin and synaptophysin) results with subcellular structure are still very useful in establishing cell type.

Spindle cell endocrine carcinoma of the mammary gland

We report the pathological characteristics of a variant of mammary endocrine tumour, predominantly formed from cytologically bland spindle cells. This neoplasm grows as a red, well defined mass lacking the usual macroscopical characteristics of breast cancer. Within smoothly contoured aggregates arranged in an insular pattern, delicate capillaries and collagen bundles support the neoplastic epithelial cells. Most of the tumour cells possess a slender spindle shape and form a solid or fenestrated sheet, but a few appear cuboidal and create glands. Immunohistochemical studies demonstrate that the spindle cells and the glandular cells constitute a single population. Both types of cells stain for neuroendocrine markers (chromogranin, synaptophysin, and CD 57), carcinoembryonic antigen, keratin 8/18, S-100 protein, and receptors for oestrogen and progesterone. Many of the tumour cells possess argyrophilic granules, and electron microscopy may reveal dense core granules.

Flow cytometric analysis of lung lymphocytes in lung transplant recipients

Lung transplantation is an accepted therapeutic modality in end-stage lung disease. Presently, histologic examination of tissue by transbronchial biopsy remains as the definitive diagnostic procedure for determining rejection. To begin addressing the usefulness of flow cytometric analysis of bronchoalveolar lavage fluid (BALF) in acute lung rejection, we prospectively studied the expression of markers on lymphocytes from BALF samples removed from 10 lung and heart-lung transplant recipients and compared their pattern with that of BALF lymphs obtained from normal volunteers (Norm) and nonrejecting heart transplant recipients (HT) who were receiving similar immunosuppressive regimens. Compared with both Norm and HT subjects, CD4+ lymphocytes in the BALF of lung transplant recipients was significantly reduced. A greater percentage of the CD4+ lymphocytes in nonrejecting lung transplant subjects also expressed the interleukin-2 receptor, but only during the early post-transplant period, suggesting possible reactivity to persistent donor cells. However, the CD8+ lymphocytes were increased only in lung transplant recipients undergoing acute lung rejection. We conclude that the immunologic milieu is indeed altered in the transplanted lung. Further studies in lung transplant recipients are required to evaluate the role of flow cytometry in the early detection of acute lung rejection.

Solid papillary carcinoma of the breast. A form of intraductal carcinoma with endocrine differentiation frequently associated with mucinous carcinoma

We report 20 examples of a distinctive form of intraductal papillary carcinoma frequently associated with both mucinous carcinoma and infiltrating ductal carcinoma, not otherwise specified. All the patients were in the seventh decade of life or older. The clinical presentation and macroscopic appearance suggested a benign lesion in most cases. The tumors grew in a solid papillary pattern and displayed low-grade cytological features as well as intracellular and extracellular mucin. Endocrine differentiation was demonstrated by the Grimelius stain in 11 of 17 cases and by the chromogranin immunohistochemical technique in eight of 14 cases. Lymph node metastases were not observed, but pulmonary metastasis occurred in one case. All the tumors were positive for estrogen receptors. We postulate that these lesions are the preinvasive counterpart of mucinous carcinomas with endocrine differentiation.

Fibroma and giant cell tumor of tendon sheath: a comparative histological and immunohistological study

Giant cell tumor of tendon sheath (GCTTS; "nodular tenosynovitis") and fibroma of tendon sheath (FTS) have traditionally been considered to be two points in a single neoplastic continuum. However, no systematic studies have addressed this concept directly to date. To more clearly define their relationship to one another, we studied five FTSs and seven typical GCTTSs by light microscopy and paraffin section immunohistochemistry. Tissue samples were stained for vimentin, desmin, smooth muscle actin (SMA), S100 protein, leukocyte common antigen (CD45), CD68 antigen (KP1), HAM56 antigen, alpha-1-antichymotrypsin (AACT), and MAC387 antigen. These reagents were chosen to address proposed "fibrohistiocytic" and myofibroblastic lineages for the two lesions. All tumors had a lobular appearance. GCTTS was more cellular than FTS; it contained conspicuous numbers of osteoclast-like cells, and the stroma was not extensively hyalinized. In contrast, FTS was matrix-rich, often with extensive stromal sclerosis, and contained only rare giant cells. Immunophenotyping of GCTTS showed that both the spindle cell and giant cell components were positive for vimentin, LCA, CD68, HAM56, AACT, and MAC387, suggesting monocyte-macrophage-like features. Limited reactivity for desmin and SMA also implied conjoint myofibroblastic differentiation. On the other hand, FTS showed focal staining with HAM56 (all cases) and for CD68 (one case); staining for vimentin and SMA was uniformly intense and diffuse. Based on these results, we conclude that GCTTS and FTS both exhibit varying degrees of monocyte-macrophage-like and myofibroblastic differentiation. The predominance of macrophage-related determinants in GCTTS and myofibroblastic markers in FTS supports the premise that these lesions represent phenotypic extremes of a single clinicopathologic entity.

Carcinomas of the breast with endocrine differentiation: a review

The occurrence of endocrine differentiation in some mammary carcinomas seems well-established, but pathologists continue to debate its significance. Contemporary thinking suggests that endocrine tumours of the breast do not constitute a single clinicopathological entity with a consistent histogenesis but rather that endocrine differentiation represents a pathway of neoplastic development available to a range of breast cancers. This pattern of differentiation occurs in tumours with vastly different morphological appearances, such as: ductal carcinoma in situ, mucinous carcinoma, a variant of lobular carcinoma, and low grade invasive ductal carcinoma. Although such tumours share some characteristics with intestinal endocrine neoplasms, the typical pattern of intestinal carcinoid virtually never occurs in mammary lesions. Conventional microscopy permits the diagnosis in most cases. Specialized techniques (histochemistry, immunohistochemistry, and electron microscopy) can serve as the basis for diagnosis in the absence of the appropriate morphological features. Although the system of nomenclature proposed by the World Health Organization for use with endocrine tumours in other organs can be used for endocrine tumours of the breast, only a minority of lesions will fit the established criteria. Most lesions are classifiable in the conventional categories of mammary carcinomas. No special prognostic significance is attached to these tumours at the present time.

Uterine leiomyomas with high content of mast cells

We report nine cases of uterine leiomyomas with an average of more than 10 mast cells per high-power field. The clinical presentation and morphological features of the tumors did not differ from those of conventional leiomyomas. Two cases also showed eosinophilia. The adjacent myometrium did not show an increased number of mast cells. Mast cells are frequently numerous in leiomyomas, but the significance of this finding is unknown.

Spindle-cell argyrophilic mucin-producing carcinoma of the breast. Histological, ultrastructural, and immunohistochemical studies of two cases

We report two cases of neuroendocrine carcinomas of the breast displaying unusual histological features: numerous spindle cells and argyrophilic signet-ring cells. Both patients were older than 70 years, and both presented with a bloody nipple discharge. The tumor in both cases was predominantly intraductal. The tumor cells showed little pleomorphism or cytological atypia; because of the presence of spindle cells, benign diagnoses, such as ductal epithelial hyperplasia and intraductal papilloma, were considered for the in situ component. Recognition of the palisading arrangement of the peripheral cells, intracytoplasmic lumina, mitotic figures, and mucin permitted the diagnosis of intraductal carcinoma. Invasive nests composed of identical cells confirmed the diagnosis of malignancy in both cases. Our cases, along with those previously reported, suggest that neuroendocrine carcinoma with mucin production is a distinct breast tumor that usually occurs in older patients who experience bloody nipple discharge. The prognosis may be more favorable than that of the usual type of breast carcinoma. Common histological features include predominantly intraductal growth, an absence of desmoplasia, and low-grade atypia. Awareness of morphological variants of this tumor, such as those reported here, is necessary to avoid erroneous diagnoses.

Giant multilocular prostatic cystadenoma: a distinctive lesion of the retroperitoneum in men. A report of two cases

Two examples of large, multiloculated, cystic tumors that arose within the pelvis in men of 28 and 37 years of age are described. The tumors were composed of glands and cysts lined by prostatic-type epithelium lying in a hypocellular fibrous stroma. The prostatic nature of the lesions was confirmed by immunohistochemical staining of the epithelium for prostate-specific antigen and prostatic acid phosphatase. Two apparently similar lesions were found in the literature; one tumor was attached to the prostate by a pedicle, and the other arose in the retrovesical space. These tumors, for which we propose the designation "giant multilocular prostatic cystadenoma," appear to be benign, although they may recur if incompletely excised. They may pose considerable diagnostic difficulty if the prostatic nature of the epithelium is not appreciated, an error that is likely if a relationship to the prostate is not recognized. This lesion should be included in the differential diagnosis of retroperitoneal cystic tumors in men.