A rare form of lung cancer in children is associated with mutational disruption of an enzyme that generates small noncoding RNAs.

Pleuropulmonary blastoma (PPB) is a malignant neoplasm of the lung that presents in early childhood. The early form of the disease, cystic type I PPB, can be clinically and pathologically deceptive because of its resemblance to some developmental lung cysts. This study reviews 51 cases of type I PPB and 6 lung cysts from relatives of children with PPB. Type I PPB is a delicate multilocular cyst with variable numbers of primitive mesenchymal cells beneath a benign epithelial surface. Rhabdomyoblasts and cartilage nodules are seen in 49% and 40% of cases, respectively. Tumors in the youngest subset of patients, from birth to 2 months of age, are more uniform in composition and cellularity compared with those in older groups. Early tumors have a subtle transition between normal developing lung and tumor, showing bland interstitial mesenchymal cells uniformly expanding the alveolar septa. Presumed regressive changes including cyst wall necrosis are common. This phenomenon may explain the variable and sometimes sparse tumor cellularity seen in some type I PPBs. On a biologic level, this process supports the concept that not all type I PPBs are fated to progress to a type II or III PPB. Factors that control the balance between progression and regression may be important in predicting tumor behavior and determining which patients will benefit from adjuvant chemotherapy. In the meantime, recognition of this lesion as a neoplasm with malignant potential rather than a developmental cystic malformation is vital so the child can receive complete excision and appropriate follow-up care.

Embryonal rhabdomyosarcoma of the uterine cervix is an uncommon presentation of the most common soft-tissue sarcoma in the first decades of life. Unlike embryonal rhabdomyosarcoma in other anatomic sites, in which 70–80% of cases present before 9 years of age, the average age in our series of 14 cervical cases was 12.4 years (median, 13 years), with an age range of 9 months to 32 years at diagnosis. Of the 14 cases, 12 presented as a polyp at the cervical os; two patients had an infiltrative mass in the cervix without a botryoid polyp. The polyps measured 1.5–5 cm and all had the histopathological pattern of the sarcoma botryoides variant of embryonal rhabdomyosarcoma, with condensations of primitive and differentiated rhabdomyoblasts beneath the surface epithelium and around endocervical glands. Nodules of benign-appearing cartilage were present in the stroma of six cases (43%). One of the embyronal rhabdomyosarcomas from the youngest patient, 9 months old, also had a distinctive microscopic focus of immature tubular profiles in a primitive stroma; these tubules expressed epithelial and neuroendocrine markers. Two patients had a pleuropulmonary blastoma, one diagnosed 9 years before the embryonal rhabdomyosarcoma of the cervix and the other recognized synchronously. This latter 9-year old had a DICER1 germline mutation. One patient presented with hirsutism and had a Sertoli–Leydig cell tumor, an incidentally detected cervical embryonal rhabdomyosarcoma, and nodular hyperplasia of the thyroid. Although a pleuropulmonary blastoma was not documented in the latter patient, ovarian sex-cord stromal tumors and nodular hyperplasia of the thyroid are manifestations of the pleuropulmonary blastoma family tumor and dysplasia syndrome (OMIM 601200). Embryonal rhabdomyosarcoma of the cervix must be distinguished from other rare entities, including adenosarcoma, malignant mixed Mullerian tumor and low-grade stromal sarcoma, as the former has a better prognosis; 12 of our 14 patients remain disease-free following conservative surgery and chemotherapy. Our study suggests that cervical embryonal rhabdomyosarcoma may be another pathological manifestation in the spectrum of extrapulmonary pathology in the setting of pleuropulmonary blastoma.

Embryonal rhabdomyosarcoma (ERMS) is the most common sarcoma of childhood and is a component of the familial Pleuropulmonary Blastoma (PPB)-predisposition syndrome. Using the PPB model, we hypothesized that DICER1 mutations would be found in familial and sporadic forms of ERMS. Blood samples from four children with familial PPB and ERMS, and an additional 52 sporadic ERMS tumors were tested for DICER1 mutations. DICER1 mutations were found in all 4 patients with familial PPB and in 2 of 52 (3.8%) patients with sporadic ERMS. Our findings confirm the pathogenetic relationship between ERMS and PPB and suggest that ERMS may result from abnormal miRNA regulation.