Renal cell carcinoma (RCC) occurs in 2-4% of patients with tuberous sclerosis complex (TSC). Previous reports have noted a variety of histologic appearances in these cancers, but the full spectrum of morphologic and molecular features has not been fully elucidated. We encountered 46 renal epithelial neoplasms from 19 TSC patients and analyzed their clinical, pathological and molecular features, enabling separation of these 46 tumors into three groups. The largest subset of tumors (n=24) had a distinct morphological, immunological and molecular profile, including prominent papillary architecture and uniformly deficient SDHB expression prompting the novel term “TSC-associated papillary RCC.” The second group (n=15) was morphologically similar to a hybrid oncocytic/chromophobe tumor (HOCT) while the last 7 renal epithelial neoplasms of group 3 remained unclassifiable. The TSC-associated papillary RCCs (PRCC) had prominent papillary architecture lined by clear cells with delicate eosinophilic cytoplasmic thread-like strands that occasionally appeared more prominent and aggregated to form eosinophilic globules. All 24 (100%) of these tumors were the International Society of Urological Pathology (ISUP) nucleolar grade 2 or 3 with mostly basally located nuclei. Tumor cells from 17 of 24 TSC-associated PRCC showed strong, diffuse labeling for CA-IX (100%), CK7 (94%), vimentin (88%), CD10 (83%), and were uniformly negative for succinate dehydrogenase subunit B (SDHB), TFE3 and AMACR. Gains of chromosomes 7 and 17 were found in 2 tumors, whereas chromosome 3p deletion and TFE3 translocations were not detected. In this study, we reported a sizable cohort of renal tumors seen in TSC and were able to identify them as different morphotypes which may help to expand the morphologic spectrum of TSC-associated RCC.
Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms that may show overlapping morphology and immunohistochemistry with uterine smooth muscle tumors. In this study, we evaluated the morphologic, immunohistochemical, and molecular features of 32 PEComas, including 11 with aggressive behavior. Two distinct morphologies were observed: classic (n=30) and those with a lymphangioleiomyomatosis appearance (n=2). In the former, patients ranged from 32 to 77 (mean: 51) years and 13% had tuberous sclerosis. Tumors ranged from 0.2 to 17 (mean: 5.5) cm with 77% arising in the corpus. Epithelioid cells were present in 100% and a spindled component was seen in 37%. Nuclear atypia was low (53%), intermediate (17%), or high (30%). Mitoses ranged from 0 to 36 (mean: 6) and 0 to 133 (mean: 19) per 10 and 50 high-power fields, with atypical mitoses present in 30%. Thin and delicate vessels were noted in 100%, clear/eosinophilic and granular cytoplasm in 93%, stromal hyalinization in 73%, necrosis in 30%, and lymphovascular invasion in 10%. All tumors were positive for HMB-45, cathepsin K, and at least one muscle marker, with most expressing melan-A (77%) and/or MiTF (79%). A PSF-TFE3 fusion was identified in one while another showed a RAD51B-OPHN1 fusion. Follow-up ranged from 2 to 175 (mean: 41) months, with 63% of patients alive and well, 20% dead of disease, 13% alive with disease, and 3% dead from other causes. In the latter group (n=2), patients were 39 and 49 years old, one had tuberous sclerosis, while the other had pulmonary lymphangioleiomyomatosis. Both tumors expressed HMB-45, cathepsin K, and muscle markers, but lacked TFE3 and RAD51B rearrangements. The 2 patients are currently alive and well. Application of gynecologic-specific criteria (≥4 features required for malignancy: size ≥5 cm, high-grade atypia, mitoses >1/50 high-power fields, necrosis, and lymphovascular invasion) for predicting outcome misclassified 36% (4/11) of aggressive tumors; thus, a modified algorithm with a threshold of 3 of these features is recommended to classify a PEComa as malignant.
Pilomatrixoma is a common benign neoplasm of children and young adults with a female predilection. In contrast, its malignant counterpart, pilomatrix carcinoma is a rare neoplasm of older adults with a male preponderance. Pilomatrix carcinomas are locally aggressive with a tendency to recur. We report a case of a 44-year-old male who presented with an enlarging soft tissue tumor on the right upper back. Histology revealed an asymmetric, poorly circumscribed, lobulated neoplasm located deeply in the dermis with infiltration into the underlying subcutaneous tissue. The tumor was comprised of basaloid cells containing vesicular nuclei, prominent nucleoli, scant cytoplasm, and brisk mitotic activity. A focus of basaloid cells transitioning to shadow cells with central keratinized material and tumor necrosis was also present. The diagnosis of a pilomatrix carcinoma was rendered. Considering the infiltrative nature of this neoplasm with perineural and intramuscular invasion, the patient underwent 3 surgical excisions before it was completely removed.
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