Spontaneous Regression of Diffuse Periosteal Melanotic Neuroectodermal Tumor of Infancy in the Tibia, With 13-Year Follow-up

Abstract

Melanotic neuroectodermal tumor of infancy (MNTI) is a rare entity primarily affecting the craniofacial bones during the first year of life, with only 5 reported cases involving peripheral long bones. We herein present a case of MNTI in the tibia of an infant, with a somewhat atypical presentation, and a noteworthy clinical course characterized by progressive spontaneous resolution without therapy, thus sparing the child the trauma of amputation. There is no evidence of active residual or recurrent disease with 13-year follow-up. To the best of our knowledge, essentially all reported cases of MNTI have received empirical treatment, some at the price of mutilating surgery or fatal chemotherapy. We propose that the necessity of aggressive treatment be evaluated on a case-by-case basis, especially in patients with diffuse periosteal involvement, as in this patient. A trial of watchful waiting can be considered when treatment would involve substantial morbidity or risk of complications.

Case Details

Disease Location

Tibia

Personal Characteristics

7-month-old girl

Clinical Characteristics

Swelling of the left lower leg with an underlying nontender firm mass along the mid-shaft of the tibia. An x-ray showed extensive circumferential irregular hyperostosis involving most of the left tibia, suggestive of caffey disease. Biopsy was performed. This showed a background of reactive periosteal new bone interspersed with moderate fibrous connective tissue, interspersed nests of epithelioid cells with granular brown cytoplasmic pigmentation, and nonpigmented cells that often showed marked crush artifact. Immunohistochemical staining showed the pigmented epithelioid cells to be positive for cytokeratin, and the crushed or neuroblast-like cells to stain for CD56, suggesting neural differentiation. The findgins were consistent with melanotic neuroectodermal tumor of infancy (mnti). Electron microscopic study of a portion of tumor from the second biopsy showed cytoplasmic melanosomes and rare premelanosomes in the pigmented cell population, with rare dense core granules suggestive of neuroendocrine granules in an occasional nonpigmented tumor cell.

Remission Characteristics

Over the course of several years, imaging has shown continued regression of the tumor and normalization of the bone. An x-ray 2 years after diagnosis showed substantial remodeling and normalization of the bone, and imaging 6 years after diagnosis showed near-complete resolution, with a smooth although slightly irregular cortical surface

Treatment & Mechanisms

Proposed Remission Mechanisms

Stimulation of immune defenses by the debulking procedure vs. Increase in efficacy of the immune system with age.

Clinical Treatment

Biopsy