Diagnosis and behavior of juvenile rhabdomyosarcoma.

The main problems in the diagnosis of rhabdomyosarcoma are 1) distinction of undifferentiated examples from other small cell malignancies, especially soft-tissue Ewing's tumor and lymphoma; 2) distinction of spindling examples from fibrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma, polyhistioma, and other sarcomas; 3) recognition of minimal criteria on small samples such as needle biopsy specimens or frozen sections; and 4) recognition of rhabdomyosarcoma in uncommon sites such as bone (mandible), perineum, retroperitoneum, and chest. In 95 pediatric cases diagnosed and treated at Royal Alexandria Hospital for Children--45 after the introduction of combined therapy--minimal diagnostic criteria were assessed. Cross-striations were found in only one third of cases; longitudinal myofibrils were more common and more helpful. There was much overlap between histologic types, and the microscopic patterns had little bearing on prognoses in preadolescent children. Fourteen cases could not be further differentiated ("embryonal sarcoma, probably rhabdomyosarcoma")--nine small-cell tumors; four tumors from genitourinary tract or head for which very small biopsy specimens were available, and one spindling retroperitoneal neoplasm. In all, slight evidence suggested embryonal rhabdomyosarcoma; this evidence included oat-shaped nuclei and, in a few cells, deeply eosinophilic cytoplasm, small elongated processes, or myxoid or alveolar foci--features that exclude lymphoma and Ewing's tumor. In six cases that were originally classified as poorly differentiated or undifferentiated, later material confirmed the presence of rhabdomyosarcoma by showing a predominantly well-differentiated (pleomorphic) or alveolar pattern after therapy. In 14 remaining undifferentiated cases, immunoperoxidase staining with antihuman-myoglobin serum was positive in five. With combined therapy there was 100 per cent survival among patients with paratesticular, limb, and stage I and stage II tumors; considerably improved survival among patients with head and neck, pelvic, and stage III tumors; and 100 per cent mortality among patients with intra-abdominal and stage IV tumors.

Maldescent of the thymus: 34 necropsy and 10 surgical cases, including 7 thymuses medial to the mandible.

Among 3236 pediatric necropsies over 23 years, abnormal position of thymic tissue was recorded in 34 cases. Cardiac anomalies, predominantly those seen in DiGeorge syndrome, were present in 24; 3 had noncardiac anomalies only, 4 had other diseases, and 3 were sudden infant deaths. Mediastinal thymic tissue was absent in 22 cases, small or unilateral in 7, and normal in 5. The maldescended thymic tissue was unilateral in 18, bilateral in 11, and multiple on one or both sides in 5. It was situated near the thyroid gland in 19, lower in the neck in 6, and higher in 9, including 7 medial to the submandibular salivary gland and 1 at the base of the skull. The maldescended tissue approached the size of a normal lobe of thymus in eight and was 2.4 to 0.1 cm in the remainder. Over the same period, in only two cases was no thymic tissue found. Among 68,000 surgical specimens over 40 years, there were 10 cases of ectopic thymus in the neck, including 1 cutaneous and 4 cystic. This frequency of thymic tissue in the neck may explain why lymphoid tissues are sometimes relatively normal in cases of absent mediastinal thymus and behooves a search in the submandibular salivary gland region and higher before diagnosing thymic agenesis.

Epignathus, double pituitary and agenesis of corpus callosum.

Two infants from unrelated families died on the 1st day of life with epignathus, duplication of the entire pituitary, infundibulum and sella, and widening or separation of midline structures of the head including absent corpus callosum. We suggest that some infants surviving surgery for large epignathi may have relatively symptomless absent corpus callosum or double pituitary.