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Background: Perivascular tumors, which include myopericytoma and myofibroma, are rare benign soft tissue neoplasms composed of perivascular smooth muscle cells. Most demonstrate characteristic morphology and are readily diagnosed. However, a recently identified hypercellular subset shows atypical histologic features and harbor unique SRF gene fusions. These cellular perivascular tumors can mimic other more common sarcomas with myogenic differentiation. Methods: Clinical, radiological, morphological, immunohistochemical, and molecular findings were reviewed. Results: A slow-growing, fluctuant mass was noted within the philtrum at 16 months. Ultrasonography revealed a well-circumscribed cystic hypoechoic lesion. A small (1.0 cm), tan, well-circumscribed soft-tissue mass was excised after continued growth. Histologically, the encapsulated tumor was hypercellular and composed of spindle cells with predominantly-storiform architecture, focal perivascular condensation, dilated branching thin-walled vessels, increased mitoses, and a smooth muscle immunophenotype. An SRF::NCOA2 fusion was identified. Conclusion: We report the first case of an SRF-rearranged cellular myopericytoma in the perioral region in a young child. This case expands the differential diagnosis of perioral soft tissue tumors with myogenic differentiation. We highlight key clinical, pathological, and molecular features. As we illustrate, these rare tumors pose a considerable diagnostic challenge, and risk misdiagnosis as sarcoma, most notably spindle cell rhabdomyosarcoma.

Perivascular tumors, which include myopericytoma and myofibroma, are rare benign soft tissue neoplasms composed of perivascular smooth muscle cells. Most demonstrate characteristic morphology and are readily diagnosed. However, a recently identified hypercellular subset shows atypical histologic features and harbor unique SRF gene fusions. These cellular perivascular tumors can mimic other more common sarcomas with myogenic differentiation.Clinical, radiological, morphological, immunohistochemical, and molecular findings were reviewed.A slow-growing, fluctuant mass was noted within the philtrum at 16 months. Ultrasonography revealed a well-circumscribed cystic hypoechoic lesion. A small (1.0 cm), tan, well-circumscribed soft-tissue mass was excised after continued growth. Histologically, the encapsulated tumor was hypercellular and composed of spindle cells with predominantly-storiform architecture, focal perivascular condensation, dilated branching thin-walled vessels, increased mitoses, and a smooth muscle immunophenotype. An SRF::NCOA2 fusion was identified.We report the first case of an SRF-rearranged cellular myopericytoma in the perioral region in a young child. This case expands the differential diagnosis of perioral soft tissue tumors with myogenic differentiation. We highlight key clinical, pathological, and molecular features. As we illustrate, these rare tumors pose a considerable diagnostic challenge, and risk misdiagnosis as sarcoma, most notably spindle cell rhabdomyosarcoma.

Pathologic examination of young adult gynecomastia tissue is controversial given the low incidence of breast carcinoma in this population. The authors examined the pathologic findings in a large cohort of adolescents with gynecomastia to evaluate the need for routine tissue analysis in this population.A retrospective review of men who underwent unilateral or bilateral mastectomy for gynecomastia at a single institution between February of 2007 and November of 2019 identified demographics, medical history, surgical characteristics, and pathologic findings. Descriptive statistics were performed.A total of 268 male patients were included. Mean age was 16.6 years. Mean body mass index was 27.8 kg/m2, and 42.5 percent of the sample was obese. The majority (83.2 percent) underwent bilateral subcutaneous mastectomy. There were no abnormal histopathologic findings in 95.1 percent. Among the 13 patients with abnormalities, eight (3 percent) had nonproliferative changes, two (0.8 percent) had proliferative changes without atypia, two (0.8 percent) had atypical ductal hyperplasia, and one (0.4 percent) had both bilateral atypical ductal hyperplasia and unilateral ductal carcinoma in situ. No patients had invasive carcinoma. The three patients with atypical ductal hyperplasia and/or ductal carcinoma in situ were obese but had no other breast cancer or gynecomastia risk factors.Findings conferring potentially increased risk of developing breast cancer were identified in three male adolescents (1.2 percent). Incidence of these findings is similar between male adolescents and similarly aged female adolescents undergoing breast reduction surgery. Although worrisome pathology results are rare, too little is known about the natural history of atypical proliferation and ductal carcinoma in situ in young men to recommend against routine analysis.Risk, IV.

Thyroid nodules with atypia of undetermined significance (AUS) are challenging to manage because of their intermediate risk of malignancy. Subclassification of atypia can refine malignancy risk in adult AUS nodules but has not been evaluated in children.This was a retrospective cohort study of pediatric patients (19 years old) who underwent fine-needle aspiration (FNA) of a thyroid nodule with resulting AUS cytology. Atypia was subclassified as nuclear only, architectural only, nuclear and architectural, or oncocytic. The primary outcome was the association between atypia subtype and malignancy. A secondary outcome was the association of atypia subtype with repeat FNA cytology.Sixty-eight AUS nodules in 61 patients were analyzed. The median age at FNA was 16.2 years (range, 9.8-18.9 years). Twenty-four nodules (35%) were malignant. Nuclear atypia only was present in 17 nodules (25%), architectural atypia only was present in 27 nodules (40%), nuclear and architectural atypia was present in 20 nodules (29%), and predominantly oncocytic features were present in 4 nodules (6%). The presence of nuclear atypia was associated with a significantly increased rate of malignancy (22 of 37 [59%] vs 2 of 31 [6.5%]; P.001), whereas architectural atypia was not associated with malignancy (P = .8). Repeat FNA was performed in 42 of 68 nodules (62%). In nodules with initial nuclear and architectural atypia, benign repeat cytology had a high false-negative rate (3 of 6; 50%).Pediatric AUS nodules with nuclear atypia have a high rate of malignancy, but architectural atypia is not associated with malignancy. In nodules with nuclear atypia, repeat FNA may inform clinical decisions regarding the need for resection. In the absence of suspicious clinical features, nodules without nuclear atypia might be considered for observation rather than resection or repeat FNA.

Mullerian papilloma is a rare benign tumor of the cervix and/or vagina that occurs predominantly in young children. The cytologic features of benign mullerian papilloma have never been described. We report for the first time, to our knowledge, the cytologic findings of a benign mullerian papilloma from the vaginal fluid specimen of a 15-mo-old girl using touch prep, ThinPrep, and cell block preparations. The deceptive cytologic features of a cellular specimen with complex papillary fronds composed of overlapping and crowded small hyperchromatic cells, with a high nuclear:cytoplasmic ratio, and feathering in this case resembled a malignant neoplasm. The clinical findings and cytomorphology of a benign mullerian papilloma can mimic those of malignant lesions of the female lower genital tract such as sarcoma botryoides and adenocarcinoma. An awareness of this entity and its potential to mimic these more aggressive neoplasms is essential for accurate diagnosis and to avoid over-treatment.