This video, presented by Jared Gardner and Dr. Edie Fulton, provides a detailed pathology review of Inclusion Body Fibromatosis, also known as Infantile Digital Fibroma. This benign fibroblastic proliferation primarily affects the digits of infants, often presenting on the 2nd, 3rd, or 4th fingers/toes, with some cases present at birth. Microscopically, it is characterized by fascicles of bland spindle cells within the dermis, distinguished by the presence of eosinophilic, actin-rich cytoplasmic inclusion bodies adjacent to the nucleus. The video emphasizes the importance of clinical context and these specific microscopic findings for diagnosis, differentiating it from other fibromatoses. While benign and not malignant, the lesion has a notable tendency for local recurrence, often attributed to the anatomical challenges of complete surgical excision in the limited space of the digits. A second case highlights a more subtle presentation, reinforcing the diagnostic significance of the inclusion bodies.
Exploring Inclusion Body Fibromatosis: A Pediatric Digital Lesion
0:00 Introduction to Inclusion Body Fibromatosis: Jared Gardner and Dr. Edie Fulton introduce Inclusion Body Fibromatosis, also known as Infantile Digital Fibroma or Infantile Digital Fibromatosis, highlighting the common confusion caused by multiple names.
0:31 Unique Clinical Presentation: This benign entity typically presents as a nodule on the fingers or toes of babies, with a predilection for the 2nd, 3rd, and 4th digits, usually on the dorsal aspect in the middle to distal portion. About 30% are congenital, with the rest developing within the first year of life.
1:07 Microscopic Features - Fibroblastic Proliferation: Histologically, it's a fibroblastic proliferation filling the dermis and sometimes extending into the subcutis, characterized by fibroblasts arranged in weaving fascicles.
1:31 Differential Diagnosis - Distinct from Other Fibromatoses: It's important to note that this condition is unrelated to desmoid fibromatosis or palmar/plantar fibromatosis, which typically occur in adults, are deeper-seated, and attach to tendons.
3:09 Key Diagnostic Feature - Cytoplasmic Inclusion Bodies: The defining characteristic is the presence of bright red or pink, globule-like inclusion bodies within the cytoplasm of the fibroblasts, located next to the nucleus. These are condensed actin filaments.
3:53 Diagnosis Based on H&E and Clinical History: The diagnosis can almost always be made on H&E-stained slides combined with the typical clinical history (nodule on baby's digits, bland fibroblastic spindle cells, and inclusion bodies), making immunostains generally unnecessary.
4:07 Special Stains (Optional): If needed, special stains like PTAH (Phosphate Tungstic Acid Hematoxylin) can highlight the inclusion bodies in dark purple, and Trichrome stain will color them bright red.
5:11 Prognosis and Local Recurrence: Inclusion Body Fibromatosis is benign and not malignant, but it has a tendency for local recurrence. This is often attributed to the conservative nature of surgical excisions on digits, where space is limited and full lesion removal without compromising other structures can be challenging.
6:46 Second Case Example (Subtle Presentation): A second case illustrates that the fascicular pattern may be less dramatic, and the inclusion bodies can be more subtle, requiring careful searching to identify them for an accurate diagnosis.