Omental mesenteric myxoid hamartoma, a subtype of inflammatory myofibroblastic tumor? Considerations based on the histopathological evaluation of four cases

Biliary Atresia Remnants Revisited: Myogenesis, Hepatic Duct-Like Structures, and Fate of Peribiliary Glands

PURPOSE AND CONTEXT

Proximal levels of excised remnants from youngest infants may reveal early features of biliary atresia (BA).

METHOD

A targeted IHC survey was applied to 34 most proximal 2 levels in 17 BA remnants excised at age 10-74 days including 7 = <30 days old and 6 control hepatic ducts (HD).

KEY RESULTS

Severity of inflammation and extent of active fibroplasia do not distinguish proximal remnants in younger (n = 7) and older (n = 10) infants. In 27/34 levels of 14/17 remnants, reactive stroma is focally SM-MHC-2 (+), marking smooth muscle myosin, termed reactive myogenesis (RM), that is absent in controls. RM facilitates identification of 3 novel hepatic duct remnants (HDR): an HD-like collagen collar lined by degenerating cholangiocytes (n = 5); erosion defects in loose reactive stroma (n = 14); solitary foci of hyperplastic squamoid epithelium (n = 4). Peribiliary glands are either hyperplastic or atretic and typically lack RM.

CONCLUSION

Minimally inflammed end-stage lesions in BA remnants occur at youngest ages favoring prenatal onset. Three novel HDR are defined. RM, a useful surrogate for HDR, is a prevalent inappropriate stromal reaction in proximal remnants of uncertain biological significance. RM is the source of mature smooth muscle in BA remnants.

Inflammatory Myofibroblastic Tumor After Treatment of Wilms Tumor in a 6-Year-Old Boy: A Case Report and Literature Review

Inflammatory myofibroblastic tumor (IMT) is a rare tumor with an indolent course. It is less often reported as a second tumor that occurs after treatment of malignant tumors in pediatric patients. Here, we report a case of IMT following Wilms tumor (WT), and conduct a literature review concerning IMTs and WT to evaluate the diagnostic possibility of IMT as a second tumor. The coexistence of the 2 tumors may cause confusion as to whether they share genetic links or that IMTs may appear as late effects of the treatment of WT.

ALK-1-positive inflammatory myofibroblastic tumor of the thyroid complicated by Hashimoto's thyroiditis: report of a rare case and a literature review

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) of the thyroid are extremely rare soft-tissue tumors. In the literature, IMTs are sometimes called plasma cell granulomas (PCGs) or inflammatory pseudotumors, which often causes ambiguity. To date, 17 cases of PCGs and five cases of thyroid IMTs have been reported. These cases reveal that IMTs of the thyroid are often negative for the anaplastic lymphoma kinase (ALK-1) gene. To provide further information on this rare lesion, we present a case of an ALK-1-positive thyroid IMT and a review of IMTs of the thyroid.

CASE PRESENTATION

A 34-year-old Chinese woman presented with a painless neck mass that had persisted for over a month. Ultrasonography revealed a 4.28 × 2.53 cm² hypoechoic mass, in the left lobe of the thyroid gland. Serum levels of thyroglobulin and anti-thyroglobulin antibodies were high. Subsequently, left lobectomy was performed. Macroscopically, the lesion was a gray-brown nodular mass with a partial envelope. Histologically, two different lesion types were observed. The first lesion showed classic spindle cell proliferation, with spindle cells arranged in fascicles, accompanied by mature inflammatory cells. The other lesion showed a large number of infiltrating lymphocytes, with lymphoid follicles in the remaining thyroid gland, which was atrophic. Immunohistochemical staining showed that the spindle cells were negative for CK19, CyclinD1, Gelectin-3, EMA, CD34, S100, Bcl-2, and STAT-6, but strongly positive for ALK-1, vimentin, and TTF1. CK was focally expressed, and the Ki-67 index was 5%. A diagnosis of IMT was proposed according to immunohistochemical findings and morphology. Hashimoto's thyroiditis was confirmed according to serum levels of thyroglobulin and anti-thyroglobulin antibodies and morphology. The patient did not receive adjuvant therapy. She remained alive without disease recurrence for 10 months after lobectomy.

CONCLUSIONS

IMTs should be considered in the diagnosis when spindle cell proliferation accompanied by mature inflammatory cells is observed, spindle cells are mildly atypical, and myofibroblast differentiation is present in the thyroid. A uniform diagnostic term is crucial to avoid ambiguity. Clinicians and pathologists should be aware of the necessity for long-term follow-up, especially in ALK-positive cases. The therapeutic potential of ALK-1 positivity should be explored further.

Infantile inflammatory myofibroblastic tumors: clinicopathological and molecular characterization of 12 cases

Inflammatory myofibroblastic tumors arising in infants are rare, poorly investigated and mostly reported as isolated cases or as a part of larger series thus, their clinicopathological and molecular features are essentially unknown. Archival files from two large pediatric institutions and a tumor registry were queried for pediatric inflammatory myofibroblastic tumors. Available material from patients ≤12 months of age was reviewed. Additional immunostains (ALK-1, D240, WT1) and ALK-FISH studies were performed as needed. Targeted anchored multiplex PCR with next-generation sequencing was done in all cases. A total of 12 of 131 infantile cases (mean 5.5 months) were identified (M:F of 2:1). Anatomic locations included intestinal/mesenteric (n = 6), head/neck (n = 3), and viscera (n = 3). Half of tumors showed a hypocellular myxoid pattern, perivascular condensation, and prominent vasculature with vague glomeruloid structures present in four of them. The remaining cases exhibited a more cellular pattern with minimal myxoid component. ALK-1 immunohistochemistry was positive in most cases (11/12) with cytoplasmic-diffuse (n = 6), cytoplasmic-granular (n = 2), and dot-like (n = 3) staining patterns. ALK fusion partners identified in five cases included EML4, TPM4, RANBP2, and a novel KLC1. Three inflammatory myofibroblastic tumors showed fusions with other kinases including TFG-ROS1 and novel FN1-ROS1 and RBPMS-NTRK3 rearrangements. Favorable outcome was documented in most cases (10/11) with available follow-up (median 17 months) while three patients were successfully treated with crizotinib. In summary, infantile inflammatory myofibroblastic tumors are rare and can exhibit paucicellular, extensively myxoid/vascular morphology with peculiar immunophenotype mimicking other mesenchymal or vascular lesions. All tumors harbored kinase fusions involving ALK, ROS1, and NTRK3 including three novel fusion partners (KLC1, FN1, and RBPMS, respectively). A favorable response to crizotinib seen in three cases supports its potential use in infants as seen in older patients. Awareness of these unusual morphologic, immunophenotypic, and molecular features is critical for appropriate diagnosis and optimized targeted therapy.

Inflammatory myofibroblastic tumor of the small intestine mimicking acute appendicitis: a case report and review of the literature

BACKGROUND

Inflammatory myofibroblastic tumor is a rare tumor of a borderline malignancy. Although it is commonly seen in children, the number of childhood cases in the current literature is limited. The lung is the most commonly affected location. However, cases that have been documented in the mesentery-omentum have mostly been located in the mesentery of the small bowel and not in the antimesenteric edge as in our patient.

CASE PRESENTATION

A 6-year-old Greek boy was referred to our hospital with acute abdominal pain mimicking appendicitis. Ultrasound and computed tomography revealed a solid mass in the abdomen. The patient underwent laparoscopic resection of the tumor, and histopathology and immunohistochemical analysis favored an omental-mesenteric myxoid hamartoma, which is a variant of an inflammatory myofibroblastic tumor. The patient's postoperative course was uneventful, and he has been asymptomatic during follow-up.

CONCLUSIONS

Inflammatory myofibroblastic tumor of the small intestine is a rare, benign neoplasm in children that should be considered as a possible cause of acute abdomen. A precise diagnosis can be made on the basis of histologic findings. Surgical excision is the treatment of choice.