Peripheral T cell lymphomas are rare in young patients. We report the first case of a follicular variant of peripheral T cell lymphoma not otherwise specified in an 11-year-old boy, who presented with a large mediastinal mass. Microscopic examination of the mediastinal biopsy revealed nodular infiltration of medium- to large-sized atypical lymphocytes. Immunohistochemistry showed expression of follicular helper T cell markers (CD10, PD1, CXCL13, and BCL6) in tumor T cells. Epstein-Barr virus (EBV) was not detected by an in situ hybridization assay for EBV-encoded RNA. Interestingly, fluorescence in situ hybridization detected the presence in the tumor cells of the t(5;9)(q33;q22) translocation, involving ITK and SYK rearrangement. T cell clonality was detected by multiplex PCR analysis of TRG and TRD gene rearrangements. After 4 cycles of systemic chemotherapy, the patient was in complete remission. Although this entity is very rare, our observations show that lymphomas arising from T follicular helper cells may occur in children and that this should be distinguished from other lymphomas, such T-lymphoblastic lymphomas, which require a specific therapeutic approach.

BACKGROUND: Only 29 cases of constitutional 9q22 deletions have been published and all have been sporadic. Most associate with Gorlin syndrome or nevoid basal cell carcinoma syndrome (NBCCS, MIM #109400) due to haploinsufficiency of the PTCH1 gene (MIM *601309).
RESULTS: We report two mentally retarded female siblings and their cognitively normal father, all carrying a similar 5.3 Mb microdeletion at 9q22.2q22.32, detected by array CGH (244 K). The deletion does not involve the PTCH1 gene, but instead 30 other gene,s including the ROR2 gene (MIM *602337) which causing both brachydactyly type 1 (MIM #113000) and Robinow syndrome (MIM #268310), and the immunologically active SYK gene (MIM *600085). The deletion in the father was de novo and FISH analysis of blood lymphocytes did not suggest mosaicism. All three patients share similar mild dysmorphic features with downslanting palpebral fissures, narrow, high bridged nose with small nares, long, deeply grooved philtrum, ears with broad helix and uplifted lobuli, and small toenails. All have significant dysarthria and suffer from continuous middle ear and upper respiratory infections. The father also has a funnel chest and unilateral hypoplastic kidney but the daughters have no malformations.
CONCLUSIONS: This is the first report of a familial constitutional 9q22 deletion and the first deletion studied by array-CGH which does not involve the PTCH1 gene. The phenotype and penetrance are variable and the deletion found in the cognitively normal normal father poses a challenge in genetic counseling.