Sinonasal renal cell-like adenocarcinoma arising in von Hippel Lindau (VHL) syndrome

Sinonasal renal cell-like adenocarcinoma (SNRCLA) is a rare and relatively novel diagnosis. Hereditary and somatic genomic signatures are not well defined in this disease. We report the case of a 35-year-old African-American male with von Hippel Lindau (VHL) syndrome who developed SNRCLA. He underwent surgical resection followed by adjuvant radiation and has no recurrence one year from diagnosis. A review of the literature yielded two similar cases in the setting of VHL. In our case with associated VHL syndrome, next generation sequencing detected MST1R mutation, a possible driver. SNRCLA is an emerging tumor associated with VHL syndrome and it is hoped that future studies shed light on the underlying biology of this unique tumor.

Malignant melanotic nerve sheath tumor with PRKAR1A, KMT2C, and GNAQ mutations

Malignant melanotic nerve sheath tumor (MMNST) is a rare and potentially aggressive lesion defined in the 2021 WHO Classification of Tumors of the Central Nervous System. MMNST demonstrate overlapping histologic and clinical features of schwannoma and melanoma. MMNST often harbor PRKAR1A mutations, especially within the Carney Complex. We present a case of aggressive MMNST of the sacral region in a 48-year-old woman. The tumor contained PRKAR1A frameshift pR352Hfs*89, KMT2C splice site c.7443-1G>T and GNAQ p.R183L missense mutations, as well as BRAF and MYC gains. Genomic DNA methylation analysis using the Illumina 850K EpicBead chip revealed that the lesion did not match an established methylation class; however, uniform manifold approximation and projection (UMAP) placed the tumor very near schwannomas. The tumor expressed PD-L1, and the patient was treated with radiation and immune checkpoint inhibitors following en bloc resection. Although she had symptomatic improvement, she suffered early disease progression with local recurrence, and distant metastases, and died 18 months after resection. It has been suggested that the presence of GNAQ mutations can differentiate leptomeningeal melanocytic neoplasms and uveal melanoma from MMNST. This case and others demonstrate that GNAQ mutations may exist in malignant nerve sheath tumors; that GNAQ and PRKAR1A mutations are not always mutually exclusive and that neither can be used to differentiate MMNST or MPNST from all melanocytic lesions.

Microsecretory Adenocarcinoma of Salivary Glands: An Expanded Series of 24 Cases

Microsecretory adenocarcinoma (MSA) is a recently described salivary gland tumor with a characteristic histologic and immunophenotypic profile and recurrent MEF2C-SS18 fusions. Because only six cases of MSA have been published, its complete clinicopathologic spectrum is unclear, and its biologic behavior has not been documented. Here, we present an updated and expanded experience of 24 MSA cases. All cases of MSA were obtained from the authors' files. Immunohistochemistry for S100, SOX10, p63, p40, SMA, calponin, and mammaglobin was performed. Molecular analysis was performed by targeted RNA sequencing, SS18 break apart fluorescence in situ hybridization, and/or reverse transcriptase polymerase chain reaction for MEF2C-SS18 fusion. Clinical follow-up was obtained from medical records. A total of 24 MSA cases were collected, from 13 women and 11 men, ranging from 17 to 83 years (mean 49.5 years). The vast majority (23 of 24) arose in the oral cavity, with the palate (n = 14) and buccal mucosa (n = 6) as the most frequent subsites. Tumors showed consistent histologic features including: (1) microcystic tubules, (2) flattened intercalated duct-like cells, (3) monotonous oval hyperchromatic nuclei, (4) abundant basophilic luminal secretions, (5) fibromyxoid stroma, and (6) circumscribed borders with subtle infiltration. The tumors were very consistently positive for S100 (24 of 24), p63 (24 of 24), and SOX10 (14 of 14) and negative for p40 (0 of 21), calponin (0 of 12) and mammaglobin (0 of 16), while SMA (4 of 20) was variable. MEF2C-SS18 fusion was demonstrated in 21 of 24 cases; in the remaining 3 cases with insufficient RNA, SS18 break apart FISH was positive. Treatment information was available in 17 cases, all of which were managed with surgery only. In 14 cases with follow-up (1-216 months, mean 30), no cases recurred or metastasized. MSA is a distinct salivary gland neoplasm with remarkably consistent clinical, histologic, immunophenotypic, and genetic features that generally behaves in an indolent manner following surgery alone. These observations solidify MSA as a unique, low-grade salivary gland carcinoma that warrants inclusion in the next version of the WHO classification of head and neck tumors.