Molecular Profiling of Syringocystadenocarcinoma Papilliferum Reveals RAS-Activating Mutations.

CONTEXT.­: Syringocystadenocarcinoma papilliferum (SCACP) is a rare adnexal carcinoma and the malignant counterpart of syringocystadenoma papilliferum (SCAP), which is commonly located on the head and neck and may arise in association with a nevus sebaceus. RAS mutations have been identified in both SCAP and nevus sebaceus. OBJECTIVE.­: To evaluate the clinicopathologic and molecular features of SCACPs, which have not been previously explored. DESIGN.­: We obtained 11 SCACPs from 6 institutions and reviewed the clinicopathologic features. We also performed molecular profiling using next-generation sequencing. RESULTS.­: The cohort comprised 6 women and 5 men with ages ranging from 29 to 96 years (mean, 73.6 years). The neoplasms occurred on the head and neck (n = 8; 73%) and extremities (n = 3; 27%). Three tumors possibly arose in a nevus sebaceus. A total of 4 cases showed at least carcinoma in situ (adenocarcinoma, n = 3; squamous cell carcinoma [SCC], n = 1), and 7 cases were invasive (SCC, n = 5; mixed adenocarcinoma + SCC, n = 2). A total of 8 of 11 cases (73%) had hot spot mutations consisting of HRAS (n = 4), KRAS (n = 1), BRAF (n = 1), TP53 (n = 4), ATM (n = 2), FLT3 (n = 1), CDKN2A (n = 1), and PTEN (n = 1). All 4 cases with HRAS mutations occurred on the head and neck, whereas the KRAS mutation occurred on the extremity. CONCLUSIONS.­: RAS-activating mutations were detected in 50% of the cases, of which most (80%) involved HRAS and occurred on the head and neck, which shows overlapping features with SCAP, supporting that a subset may arise as a result of malignant transformation and likely an early oncogenic event.

Localised chronic fibrosing vasculitis versus erythema elevatum diutinum.

A woman in her 70s was referred for a painless plaque on the shin, present for 2 years and progressing in thickness. Examination revealed a large erythematous to violaceous indurated plaque with cobblestone appearance. Biopsy revealed an inflammatory infiltrate of neutrophils with scattered histiocytes, lymphocytes, eosinophils and plasma cells interspersed with areas of lamellar fibrosis and focal areas of vascular damage, suggestive of a localised chronic fibrosing vasculitis of the skin. Localised chronic fibrosing vasculitis is a rare dermatosis, typically presenting as ulcerated violet-red nodules, which can appear histologically similar to erythema elevatum diutinum (EED), which typically presents as red-brown annular plaques. EED may have a predominance of neutrophils and granulomas, while chronic fibrosing vasculitis may have a sparse infiltrate of mixed inflammatory cells without granulomas. While dapsone is a first-line treatment for EED, there are no formal guidelines on the treatment of localised chronic fibrosing vasculitis. Given the neutrophils in this sample and similarities with EED, this patient was treated with oral dapsone, resulting in plaque improvement.

Cutaneous metastases of follicular thyroid carcinoma: a report of four cases and a review of the literature.

Cutaneous metastasis of follicular carcinoma of the thyroid is very rare, and when it occurs, can exhibit a variety of histologic appearances. The 4 cases presented here were identified from the surgical pathology files of the James Homer Wright Laboratories of Pathology at the Massachusetts General Hospital (MGH). The cases consisted of 4 patients, 3 men and 1 woman, aged 52 to 75 years, with cutaneous metastasis of follicular thyroid carcinoma. The tumors include a conventional follicular carcinoma, a follicular carcinoma with anaplastic transformation following initial metastasis, the first reported cutaneous metastases of a follicular carcinoma with oncocytic features (Hürthle cell carcinoma), and a follicular carcinoma with a prominent insular carcinoma component. All 4 tumors were widely invasive within the thyroid gland. Sites of dermal metastases included a post-thyroidectomy scar, scalp, and sacral skin. Three metastases retained the morphologic and immunocytochemical features of the primary thyroid tumors. However, in one case there was high-grade transformation to anaplastic carcinoma following treatment of a sacral metastasis with accompanying loss of the characteristic immunophenotype of follicular thyroid carcinoma. Awareness of the varied morphologies of metastatic follicular thyroid carcinoma to the skin may prompt immunohistochemical analysis and the request for a complete clinical history, ultimately preventing misdiagnosis.