Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital malformation involving the dermis and subcutaneous tissue, of which there were 62 reported cases through 2014. We report RMH in two neonates presenting as a sacral skin tag. In both cases, magnetic resonance imaging (MRI) of the spine showed evidence of spinal dysraphism, including a lipomyelomeningocele and a tethered cord. Surgical repair of the defects was performed. Histopathologic examination of the skin tags showed a haphazard arrangement of mature skeletal muscle fibers and adnexal elements, consistent with RMH. The second patient also had a hemangioma on the sacrum and was diagnosed with LUMBAR (lower body hemangioma and other cutaneous defects, urogenital anomalies/ulceration, myelopathy, bony deformities, anorectal/arterial anomalies, and renal anomalies) syndrome, an association between cutaneous infantile hemangiomas of the lower body and regional congenital anomalies. The apparent association of paraspinal RMH with spinal dysraphism suggests that aberrant migration of mesodermally derived tissues (including skeletal muscle fibers) during neural tube development may be responsible for the pathologic findings in the skin. Additional study of patients with spinal dysraphism and congenital cutaneous lesions may further support this hypothesis.

ALK rearrangements occur in up to 10% of spitzoid melanocytic neoplasms. No reported cases have shown homozygous deletion of 9p21 (CDKN2A) or gains of 6p25 (RREB1) or 11q13 (CCND1), which have been associated with aggressive clinical behavior. Here we report 2 unique cases. Case 1 occurred in a 9-year-old male with a 14-mm nodule on the anterior left thigh. Biopsy revealed an ALK-positive Spitz tumor containing an irregular nodule of densely packed melanocytes with increased mitoses and loss of p16 immunoreactivity. FISH analysis showed homozygous deletion of 9p21 and gain of 6p25. Sentinel lymph node biopsy revealed small subcapsular foci of tumor. Case 2 occurred in a 7-year-old female with a 12-mm nodule on the anterior right ankle. Biopsy revealed an ALK-positive Spitz tumor containing an expansile nodule of pleomorphic epithelioid melanocytes with numerous mitoses and loss of p16 immunoreactivity. By FISH, the nodule showed homozygous deletion of 9p21 and gains of 6p25 and 11q13. Our cases show the transformation of tumors produced by an activating kinase fusion gene (ALK) through secondary genetic changes including loss of tumor suppressor activity (CDKN2A). Long-term follow up will be important to further define the behavior of these unique Spitz tumors.

Blast phase CML in TKI- and non-TKI-treated patients differs in the morphology and immunophenotype of blasts, cytogenetic findings, and associated findings in the peripheral blood and bone marrow.