Concurrent Congenital Fibrolipomatous Hamartoma and Congenital Nevus of Infancy: A Syndromic or Chance Association.

Congenital nevi and fibrolipomatous hamartoma are benign tumors of childhood, the latter being very uncommon. Fibrous hamartoma of infancy typically occurs in <2 years of life. The concurrence of these two lesions is extremely rare. We report a case of congenital fibrolipomatous hamartoma and congenital nevus of infancy in a 6-month-old male infant. Clinically, a suspicion of benign versus malignant lesion beneath the giant congenital nevus prompted its surgical removal. The histopathology confirmed it to be a compound lesion with benign melanocytic nevi and fascicles of spindle cells with eosinophilic cytoplasm representing hamartoma. Several types of melanocytic combined lesions have been noted with neuroectodermal and mesenchymal components. Sometimes, malignant soft-tissue neoplasm such as liposarcoma, rhabdomyosarcoma, and ganglioneuroblastoma do occur. This case report highlights the role of prompt surgical excision and histopathological examination.

INTRODUCTION

The term “fibrolipomatous hamartoma of infancy (FLHI)” was described by Larralde de Luna et al.[1] in 1990. They described this lesion in precalcaneal region and coined them “pedal papules in the newborn.” Enzinger in 1965[2] described 30 cases of fibrous hamartoma of infancy (FHI) which were almost similar in morphology. Congenital melanotic nevi (CMN) and FLHI are benign tumors of childhood, the latter being very uncommon. FLHI typically occurs in <2 years of life.[1] The concurrence of these two lesions with fibromatosis is rarely reported in the literature to the best of our knowledge.

CASE REPORT

A 6-month-old male infant with a giant, hairy lesion in the gluteal region measuring 7 cm × 6 cm with a satellite nodule measuring 2.5 cm × 2 cm presented to the outpatient department. The parents noticed a soft nodule in the gluteal region since birth, and the cosmetic concern brought them to the hospital. There was no associated developmental delay, and the child had achieved all milestones for his age.

Clinically, the hairy lesion was suspected to be congenital nevus; however, a benign versus malignant nodule within the giant congenital nevus prompted its surgical removal. Grossly, three fragments were received largest measuring 3 cm × 3 cm × 2.5 cm and smallest measuring 2 cm × 2 cm × 1 cm, all were covered by pigmented skin [Figure 1a]. The cut surface revealed a gray-white fibrotic unencapsulated area with yellowish appearance focally within the dermis. Multiple sections were taken and processed routinely for hematoxylin and eosin stain. Histopathology showed benign melanocytic nevus with clusters of nevus cells in the dermis extending around the hair follicles and reaching hypodermis. The nevus cells had round-to-oval nuclei and were spindly as it reached lower dermis [Figure 1b]. Underneath the benign nevus, the deeper dermis showed fascicles of bland-looking mature spindle cells with eosinophilic cytoplasm admixed with primitive-looking mesenchyme in a myxoid background. The whole of these lesions had interdigitating extensions and were seen entrapping the lobules of mature adipocytes [Figure 1c and d]. Extensive areas of fibroblastic proliferation with bland-looking spindle nuclei and moderate cytoplasm were noted at the periphery simulating fibromatosis. The lesion was poorly circumscribed and had finger-like margins extending to the adjacent soft tissues; however, it was completely excised, and margins were free.

Figure 1

(a) Resected specimen shows pigmented overlying skin which is wrinkled and thickened (b) Cut surface shows a relatively circumscribed soft-tissue tumor (c) Dermal aggregates of pigmented nevus cells (H and E, ×200) (d) Fibrolipomatous lesion in the underlying dermis (H and E, ×200)

On immunohistochemistry, the nevi cells were positive for S-100 and Melan A. The overlying epidermis was normal. The child was on follow-up for the past 1 year and was doing well without any recurrence or progression of the disease.

DISCUSSION

The FLHI is a benign tumor of the subcutis and lower dermis, usually occurs within 2 years of life, however, nearly 25% may occur congenitally.[2] Previous studies have described rare combined lesions consisting of combined neuroectodermal and mesenchymal lesions, for example, neuroectodermal benign tumors (schwannoma and ganglioneuroma) or mesenchymal tumors (e.g., cartilage or smooth muscle or skeletal muscle).[34] Müller et al.[5] described a first case report of the synchronous occurrence of CMN and FLHI and our case being the second one to the best of our knowledge.

The FHI appears as nodular lesion below the skin which are of variable sizes <2 cm to >10 cm. Usually they are asymptomatic, and surgical excision is the treatment of choice. Some of the close differential diagnosis mimicking FHI includes both benign and malignant lesions. However, they can be differentiated after excision by their subtle histopathologic features. Some of the benign lesions mimicking FHI described by Saab et al.[6] are fibrolipoma (fibrous tissue without mesenchyme), lipoblastoma (lobulated architecture), myofibroma (perivascular pattern without adipose tissue), and cellular schwannoma (spindle cells without adipose tissue). The malignant lesions which can mimic FHI include spindle cell neoplasm such as malignant peripheral nerve sheath tumor and fibrosarcoma; however, they have nuclear atypia and significant mitosis which is uncommon in FLHI.[6]

The index case had concurrent FLHI and CMN. The size of the CMN is a prognostic feature for the development of melanoma. Based on size, CMN can be divided into small (<1.5 cm), larger (>20 cm), and medium (1.5–19.9 cm), the highest risk of developing melanoma being with larger CMN. In addition to the size, satellite nodules and truncal location are other risk factors for melanoma.[3] Approximately, half of the malignancies that have occurred in larger CMN developed in the first 3 years of life, 60% by childhood, and 70% by puberty. Infants with larger CMN and more than three satellite nevi are at increased risk for malignant melanoma. The early detection of melanoma is difficult as approximately two-thirds of arise deep within the dermal and subcuticular portion of the nevus, retroperitoneum, and central nervous system.[3] The present case falls in medium-risk category based on size and associated with satellite nodule.

The pathogenesis underlying FLHI within a congenital nevus is unclear. Cytogenetically, FLHI shows reciprocal translocation t (2;3) (q31; q21),[7] complex translocations involving chromosomes 6, 8, and 12 t (6;12;8) (q25; q24.3; q13),[8] and complex structural rearrangements involving chromosomes 1, 2, 4, and 17[9] but none of them is specific. To explain the pathogenesis of simultaneous occurrence of FLHI and congenital nevus, various hypotheses have been described. According to the “dermal precursor model” of nevogenesis, which favors quiescent dermal or circulating precursor cells/stem cells as the origin of dermal nevi depending on the underlying mutation (NRAS/BRAF mutation in congenital nevi, HRAS mutation in Spitz nevi, and GNAQ mutations in blue nevi);[10] the combination of FLHI and congenital nevus could reflect just two distinctive routes of differentiation of the same stem cell.

Our case is unique in that it is the second similar case described in the English literature.

The concurrence of these two lesions could be the result of a chance association. However, as described above, few studies have tried to explain and associate their common origin. Although the genetics of these lesions is complex and difficult to reestablish in index case, syndromic associations are not excluded.

CONCLUSION

We describe an extremely rare occurrence of FLHI and medium-risk CMN in a 6-month-old child. FLHI is a benign condition of infancy and may be associated with other lesions; hence, the clinicians should be aware of these associations. A histopathological confirmation is required to rule out malignancy. Usually, no treatment is required; however, wide local excision for cosmetic reasons or suspicion of malignancy is the treatment of choice.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.