PD-L1 expression in inflammatory myofibroblastic tumors

Inflammatory myofibroblastic tumor is a rare mesenchymal tumor occurring at many anatomic sites, with a predilection for children and young adults. Often indolent, they can be locally aggressive and can metastasize, resulting in significant morbidity and mortality. Therapeutic options are often limited. The identification of underlying kinase mutations has allowed the use of targeted therapy in a subset of patients. Unfortunately, not all tumors harbor mutations and resistance to tyrosine kinase inhibitor therapy is a potential problem. We hypothesized that these tumors may be amenable to PD-L1 therapy given the immune nature of the tumor. PD-L1 expression in inflammatory myofibroblastic tumors has not yet been defined. The purpose of this study was to explore PD-L1 expression in inflammatory myofibroblastic tumors, as adaptive PD-L1 expression is known to enrich for response to anti-PD-1/PD-L1 therapies. Expression of PD-L1 (clone SP142) was assessed in 35 specimens from 28 patients. Positivity was defined as membranous expression in ≥5% of cells and evaluated separately in tumor and immune cells. Adaptive vs. constitutive patterns of tumor cell PD-L1 expression were assessed. PD-L1 status was correlated with clinicopathologic features. CD8+ T cell infiltrates were quantified by digital image analysis. ALK status was assessed by immunohistochemistry and/or FISH. Twenty-four (69%) tumors had PD-L1(+) tumor cells and 28 (80%) showed PD-L1(+) immune cells. Most recurrent and metastatic tumors (80%) and ALK(-) tumors (88%) were PD-L1(+). Adaptive PD-L1 expression was present in 23 (96%) of PD-L1(+) tumors, which also showed a three-four fold increase in CD8+ T cell infiltration relative to PD-L1(-) tumors. Constitutive PD-L1 expression was associated with larger tumor size (p = 0.002). Inflammatory myofibroblastic tumors show frequent constitutive and adaptive PD-L1 expression, the latter of which is thought to be predictive of response to anti-PD-1. These data support further investigation into PD-1/PD-L1 blockade in this tumor type.

Dermatomyofibromas presenting in pediatric patients: clinicopathologic characteristics and differential diagnosis

Dermatomyofibroma represents a rare benign fibroblastic/ myofibroblastic cutaneous tumor that mostly occurs in young adult women. It has been seldom reported in pediatric patients. In this analysis, the clinical, histopathological and immunohistochemical findings of 12 dermatomyofibromas occurring in patients up to 16 years of age are compared with those reported in adults. Six patients were male and six were female. Nine lesions were located on the neck, two on the back and one involved the chest. The usual presentation was as an asymptomatic plaque composed of bland spindled cells arranged in dermal fascicles that were oriented parallel to the epidermis. Immunohistochemically, the lesional cells expressed calponin in 11 cases, smooth muscle actin in six and muscle-specific actin in three. In contrast to prior reports from adults, dermatomyofibromas in pediatric patients do not show a female predilection. In addition, they are mostly located on the neck (56%), while in adults the most frequent location is the shoulder (35%). Dermatomyofibromas seem to stabilize after an initial period of enlargement. Punch biopsy and clinical follow up could be an alternative approach to the surgical excision in some cases of dermatomyofibroma, particularly in instances in which surgery might inflict cosmetic defects.

[Infantile myofibroma and myofibromatosis: clinical and morphologic assessment of eighteen cases]

Infantile myofibroma (myofibromatosis) (IM) is a mesenchymal tumor of soft tissues of the head, extremities and trunk. It is characterized by relapse-free infiltrative growth. It consists of neoplastic myofibroblasts at varying stage of cell differentiation which form multi-structured tumor zones. IM's morphological differentiated diagnosis is established vis-a-vis other varieties of tumor and reactive nodular structures of fibroblasts, primarily, infantile hemangiopericytomas and desmoid fibromatosis. Immunohistological and ultrastructural examination of tumor is required for making correct diagnosis of IM.

Myofibroma of the external auditory canal: report of an adult case

Myofibroma of the external auditory canal: report of an adult case.

OBJECTIVE

Myofibroma is a benign fibrous proliferative disease generally reported to occur in neonates and children. Similar lesions have been reported in adults, but solitary tumours affecting the external auditory canal are extremely rare. Only one such case has been reported in the literature.

CASE REPORT

The case of solitary myofibroma occurring in the external auditory canal of a 42-year-old woman is presented. The diagnosis of myofibromatosis was made on the basis of its histological appearance and corroborated by immunohistochemical staining.

CONCLUSIONS

Clinicians and pathologists must be aware that myofibromatosis may occur in adults at extremely rare locations. Myofibroma should be included in the differential diagnosis of fibrous lesions in the external auditory canal.

Gingival myofibroma in children: report of 4 cases with immunohistochemical findings

Oral myofibroma is a rare tumour which usually occurs in children and has been reported in the mandible, tongue, buccal mucosa with only a few cases reported from the gingiva. It appears alarming clinically due to its fast growth which may mimic a malignancy. However, it is completely benign and is usually treated by complete surgical excision with excellent prognosis. Clinically, myofibroma presents as a single swelling when it occurs on the gingiva, and more common lesions such as fibrous epulis, pyogenic granuloma and peripheral odontogenic fibroma, myofibroma are usually considered in the differential diagnosis. We present 4 additional cases of gingival myofibroma in children. Their ages ranged from 7 to 14 years. Three were girls and 1 patient was a boy. All presented with solitary gingival growths, ranging from 3 weeks to 2 months in duration, and raised the clinical diagnoses of peripheral giant cell granuloma, pyogenic granuloma and fibrous epulis. Histopathology of incisional biopsies revealed proliferation of streaming and whorled fascicles of spindle cells around slit-like vascular spaces. The spindle cells were cytologically bland and were immunopositive for vimentin and smooth muscle actin, but were negative for desmin and S-100 protein. All were treated by surgical excision.

Utility of ALK-1 protein expression and ALK rearrangements in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell lesions of the urinary bladder

Inflammatory myofibroblastic tumor of the urinary bladder is an unusual spindle cell neoplasm that displays cytologic atypia, infiltrative growth and mitotic activity mimicking malignant tumors, such as leiomyosarcoma, rhabdomyosarcoma and sarcomatoid carcinoma. The objective of this study was to determine if anaplastic lymphoma kinase (ALK-1) protein expression detected by immunohistochemistry and ALK rearrangements detected by fluorescence in situ hybridization (FISH) were useful in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell tumors of the urinary bladder. In inflammatory myofibroblastic tumor, ALK-1 expression was identified in 13 of 21 cases (62%) and ALK rearrangements in 14 of 21 cases (67%). All cases of inflammatory myofibroblastic tumor demonstrating ALK-1 expression, carried ALK rearrangements. One case negative for ALK-1 expression exhibited ALK rearrangement. ALK rearrangements were more common in women (P=0.0032). Leiomyosarcoma, sarcomatoid carcinoma, embryonal rhabdomyosarcoma and reactive myofibroblastic proliferations were negative for ALK-1 protein and ALK rearrangements. Immunohistochemistry using markers of muscle, epithelial, neural, and follicular dendritic cell differentiation showed overlap between inflammatory myofibroblastic tumor with and without ALK gene rearrangements, and between inflammatory myofibroblastic tumor and spindle cell malignancies. However, coexpression of cytokeratin and muscle-specific antigens was unique to inflammatory myofibroblastic tumor, observed in approximately half the tumors. This study indicates that detection of ALK protein and ALK gene rearrangements are useful in distinguishing inflammatory myofibroblastic tumor from spindle cell malignancies in the urinary bladder. Additionally, our findings suggest that ALK rearrangement is the primary mechanism for ALK activation and that inflammatory myofibroblastic tumor likely represents a heterogeneous group of spindle cell proliferations with the majority associated with ALK translocations, and the remaining associated with other etiologies.

ALK expression in pseudosarcomatous myofibroblastic proliferations of the genitourinary tract

AIMS

Pseudosarcomatous myofibroblastic proliferation of the genitourinary tract is rare and may develop after trauma or spontaneously. The aim of this study was to characterize further the clinicopathological features of these lesions and to examine their relationship to inflammatory myofibroblastic tumour (IMT).

METHODS AND RESULTS

Twenty-seven cases of pseudosarcomatous myofibroblastic proliferation were analysed. There were seven males and 20 females; median age was 37 years (range 16-88). Most lesions were from the bladder (n = 21), while others were in the urethra, vulva, vagina, rectum and retrovesical space. Median tumour size was 30 mm (range 6-120 mm). Seven cases (25%) had a history of prior trauma or surgery. Three cases recurred locally but not destructively. The tumours had fasciitis-like features including bland spindle cells with evenly distributed chromatin, admixed inflammatory cells (mainly lymphocytes) and often a myxoid stroma. Immunohistochemistry showed positivity for smooth muscle actin in 14/20 cases, keratin in 8/19, desmin in 7/20 and anaplastic lymphoma kinase (ALK) in 10/21 cases. Fluorescent in situ hybridization was performed in six ALK+ cases; all were negative for ALK gene rearrangement.

CONCLUSIONS

Pseudosarcomatous myofibroblastic proliferations of the genitourinary tract may show ALK immunopositivity but do not show consistent ALK rearrangement. Given subtle morphological differences and more consistently benign behaviour, their relationship to inflammatory myofibroblastic tumour at other sites remains uncertain.

Inflammatory myofibroblastic tumor of the uterus: a clinicopathologic study of 6 cases emphasizing distinction from aggressive mesenchymal tumors

Inflammatory myofibroblastic tumor (IMT) is an indolent spindle cell proliferation that can histologically resemble various malignant mesenchymal neoplasms; however, it generally behaves as a benign or locally recurrent tumor. Most IMTs involve the lung, mesentery, omentum, or retroperitoneum. We report the clinical and pathologic features of six IMTs of the uterus, one of which was included in a previous report, and emphasize the histologic and immunohistochemical features that distinguish IMTs from uterine spindle cell neoplasms that require aggressive treatment. Recently, translocations of the anaplastic lymphoma kinase (ALK) gene and immunohistochemical expression of ALK have been reported in IMTs of various anatomic sites. We compared ALK expression in uterine IMTs with that in uterine mesenchymal neoplasms with which it may be confused. Patients with IMT were between 6 and 46 years of age. None had a history of abdominal surgery; three were multiparous. The IMTs ranged from 1 to 12 cm in maximum dimension. Three grew as polypoid masses that arose in the lower uterine segment, and two of these prolapsed through the cervical os. The three other tumors grew as bulky myometrial masses with focally irregular borders and infiltrated the endometrium, parametrium, or cervical stroma. There were three main microscopic patterns: a hypocellular pattern, a fascicular pattern, and a hyalinized pattern. A lymphoplasmacytic infiltrate was present in all of the tumors, and most had a myxoid background. Mitotic activity ranged from 0 to 2 mitotic figures per 10 high power fields (HPF) except in one tumor that focally had up to 8 mitotic figures per 10 HPF. No nuclear atypia or necrosis was present. Immunohistochemical expression of ALK was present in a cytoplasmic pattern in all IMTs tested. No ALK expression was identified in uterine leiomyoma (n = 7), leiomyosarcoma (n = 6), carcinosarcoma (n = 4), endometrial stromal sarcoma (n = 4), or normal uterine tissues. Follow-up ranging from 1.5 years to 5 years in 4 patients with uterine IMTs revealed no recurrence or metastasis. IMTs should be differentiated from aggressive uterine mesenchymal tumors because they can be treated conservatively and have a more favorable prognosis. ALK expression appears to be of diagnostic value in conjunction with other immunohistochemical stains.

[Clinicopathologic characteristics of myopericytoma]

OBJECTIVE

To investigate the clinicopathologic characteristics and differential diagnosis of myopericytoma.

METHODS

Six cases of myopericytomas were analyzed by light microscopy and immunohistochemistry (LSAB detection method).

RESULTS

Tumors from 3 females and 3 males were found on the extremities and chest wall. The ages of these 6 patients ranged from 16 to 58 years. Histologically, all tumors were unencapsulated. The neoplastic cells were oval to spindle shaped with eosinophilic cytoplasm, had a myoid appearance and showd areas of concentric perivascular proliferation around lesional blood vessels which were present with focal myxoid stroma. Morphologically in some cases the tumor overlap myofibroma, hemangiopericytoma or glomus tumor. One tumor was located entirely within the lumen of a vein. In another case, the tumor displayed cellular pleomorphism, mitotic activity, necrosis should be diagnosed as malignant myopericytoma. The neoplastic cells were positive for SMA and negative for CD31, CD34, S-100, and CK.

CONCLUSIONS

Myopericytoma is composed of oval to spindle shaped myoid cells with a striking tendeny for concentric perivascular growth. These cells differentiate towards perivascular myoid cells or myopericytes. Extremely rare malignant myopericytoma exist.

ALK-1 expression in inflammatory myofibroblastic tumor of the urinary bladder

Inflammatory myofibroblastic tumor (IMT) of the bladder is an uncommon myofibroblastic spindle cell proliferation. Because of its cytologic features and infiltrative nature, it may be difficult to distinguish histologically from sarcomatous proliferations such as sarcomatoid urothelial carcinoma, leiomyosarcoma, and embryonal rhabdomyosarcoma. Recently, anaplastic lymphoma kinase (ALK) gene translocations or ALK protein expression in IMT has been reported, especially in patients of relatively young ages. However, there are only a few reports mentioning IMT of the bladder. We sought to determine the frequency of ALK expression among IMTs of the urinary bladder. We examined 16 cases of IMTof the bladder in 14 patients to elucidate the incidence of ALK-1 expression by immunohistochemistry and its diagnostic usefulness. The age of patients with IMT ranged from 18 to 76 years, with an average age of 42.8 years. The tumors from 10 of 14 patients (12 of 16 cases) were positive for ALK-1. ALK-1-positive cases ranged in age from 18 to 73 years (mean, 39.2 years; median, 38 years) and ALK-1-negative cases from 41 to 76 years (mean, 41.5 years; median, 44.5 years). Two locally recurrent cases were positive for ALK-1 in both the primary and recurrent lesion. ALK-1 immunostaining was detected only in the cytoplasm, with granular or subplasmalemmal linear features, suggesting ALK gene translocation. ALK-1 immunostaining was also performed in 8 sarcomatoid urothelial carcinomas, 5 genitourinary leiomyosarcomas, and 2 stromal tumors of uncertain malignant potential of the prostate, all of which were negative. These results support that ALK-1 immunostaining is useful to differentiate IMT from other malignant spindle cell neoplasms of the bladder. There were no histologic differences between ALK-1 positive and negative IMTs.