Expanding the Phenotype of ALK-positive Histiocytosis: A Report of 2 Cases

18F-FDG PET/CT in Pediatric ALK-Positive Histiocytosis With Isolated CNS Involvement

ABSTRACT

An 11-year-old girl presented with focal impaired awareness seizures. MRI brain demonstrated a T2 hyperintense cortical lesion in the left temporal lobe with surrounding vasogenic edema. 18F-FDG PET/CT was arranged to assess metabolic activity of the cerebral lesion, to screen the whole body for other metabolically active lesions, and to assist biopsy planning. The study demonstrated intensely increased FDG uptake within the left temporal lobe lesion without evidence of hypermetabolic lesions elsewhere on the whole-body acquisition. The brain lesion was excised, and histopathology and molecular testing were consistent with ALK-positive histiocytosis.

A male infant with ALK-positive histiocytosis recovered spontaneously

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare subtype of histiocytic neoplasm characterized by expression of ALK. We present a case of a male infant with ALK-positive histiocytosis, confirmed by pathological analysis and detection of ALK using fluorescence in situ hybridization. The boy recovered spontaneously and all the lesions completely disappeared without special treatment.

Case report: Systemic presentation of ALK-positive Histiocytosis

ALK-positive Histiocytosis (ALK-HSs) is a recently identified rare clinical entity characterized by tissue histiocytic alterations associated with ALK gene rearrangement. Clinical presentations can be solitary, multifocal, or systemic (involving multiple sites and organs). Due to limited reported cases, there is inadequate understanding of this disease. This report presents a case of ALK-HSs in a 71-year-old male patient who presented with hematuria for one week. Imaging studies conducted at an external hospital showed multiple lesions in the penis, bilateral testes, back skin, and the third lumbar vertebra. Histopathological findings included spindle and histiocytic cell proliferation with mild or indistinct cellular atypia, interstitial infiltration of lymphocytes, plasma cells, foamy histiocytes, and fibrous tissue proliferation. Immunohistochemistry of the lesion cells revealed positivity for CD68, CD163, ALK1, ALK (D5F3), and Vimentin. FISH testing indicated ALK gene separation in the lesion cells. NGS testing identified the fusion genes KIF5B(NM_004521) and ALK(NM_004304) in the lesion cells. We combined the characteristics of this case with a review of the literature to enhance our understanding of this rare clinical entity.

Multisystem ALK-positive histiocytosis: a multi-case study and literature review

BACKGROUND

Anaplastic lymphoma kinase (ALK)-positive histiocytosis, a novel rare histiocytic proliferation, was first described in 2008; it occurs in early infancy with liver and hematopoietic involvement. The spectrum was subsequently broadened to include localized diseases in older children and young adults. However, its full clinicopathological features and molecular lineage have not been fully elucidated.

RESULTS

Here, we report four cases of multisystem ALK-positive histiocytosis without hematopoietic involvement. Clinically, three patients were adults aged between 32 and 51 years. Two patients', whose main manifestations were intracranial mass and numerous micronodules in the thoracoabdominal cavity organs and skin papules respectively, had a partial response to ALK inhibitors after surgery. One patient presented with mediastinal neoplasm without surgical treatment, and progressive disease occurred after two years of ALK inhibitor therapy. The fourth patient was a 17-month-old male with a large intracranial mass and presented with a poor response to ALK inhibitor and chemoradiotherapy; he died eight months after surgery. Pathologically, the histiocytes were large, with abundant eosinophilic cytoplasm, and mixed with variable numbers of foamy cells and Touton giant cells. Interstitial fibrosis was also observed. Histiocytes were positive for macrophage markers (CD68 and CD163) and ALK. KIF5B-ALK fusions were detected in two cases, EML4-ALK in one, and both DCTN1-ALK and VRK2-ALK fusions were detected in one case.

CONCLUSIONS

We observed that ALK inhibitors present robust and durable responses in adult patients but a poor response in young children with central nervous system involvement. There is no consensus on the optimal treatment regimen and long-term prognosis requires further observation. Moreover, every unusual histiocytic proliferative lesion, especially unresectable and multisystem involvement, should be routinely tested for ALK immunohistochemical staining to identify this rare disease.

Central nervous system involvement of systemic ALK-positive histiocytosis with KIF5B-ALK fusion

ALK-positive histiocytosis is an emerging histiocytic entity that can involve a single organ or multiple organs. This disease frequently involves the central nervous system, and the importance of immunohistochemical and genetic analyses is emphasized for the accurate diagnosis of this rare entity. However, radiological findings of this disease have not been sufficiently described. Here, we report a case of a 3-year-old boy with ALK-positive histiocytosis with systemic masses that was identified to harbor KIF5B-ALK gene fusion.

A case of ALK-positive histiocytosis with multiple lesions in the unilateral breast: A case report

INTRODUCTION AND IMPORTANCE

Primary ALK-positive histiocytosis of the breast is rare. Here, we report a case of ALK-positive histiocytosis with multiple unilateral breast lesions.

CASE PRESENTATION

Our patient was a 38-year-old female with primary ALK-positive histiocytosis of the breast with multiple lesions. There were no lesions in other organs, and the patient was considered surgically resectable and underwent a left total mastectomy and sentinel lymph node biopsy. Histopathologically, there were at least three lesions in the left breast in upper inner quadrant (UIQ), upper quadrant (UQ), and upper outer quadrant (UOQ). All lesions showed spindle-shaped tumor cells that were positive for CD163 and ALK and negative for AE1/AE3. Fluorescence in situ hybridization (FISH) showed ALK and KIF5B rearrangements, suggesting the presence of the KIF5B-ALK fusion gene. In conclusion, this case was confirmed to be ALK-positive histiocytosis with multiple lesions in the unilateral breast. The patient underwent surgery and was discharged without complications.

CLINICAL DISCUSSION

Reports of ALK-positive histiocytosis are very rare, and reports of primary cases in the breast are even rarer. The basic treatment for ALK-positive histiocytosis is surgical resection; however, ALK inhibitors may be effective in unresectable or disseminated cases. Accurate diagnosis at the time of initial treatment is necessary to expand the treatment options.

CONCLUSION

This is the first case of ALK-positive histiocytosis with multiple lesions in the unilateral breast.

Failure of crizotinib based systemic treatment in ALK positive histiocytosis involving the central nervous system: a case report and literature review

BACKGROUND

Among the histiocytic disorders, anaplastic lymphoma kinase (ALK)-positive histiocytosis emerged in 2008. As more and more cases of the novel entity are reported, our understanding of it is deepened. However, only a few cases with central nervous system (CNS) involvement have been reported. Furthermore, the lesion in the suprasellar region has not been documented.  CASE PRESENTATION: We presented a case of ALK-positive histiocytosis involving the suprasellar region of a one-year-and-four-month-old boy. Through clinical, neuropathological, and genomic analyses, the patient was diagnosed with ALK-positive histiocytosis. After lesions were resected he started treatment with a combination of the three compounds vincristine, prednisolone, and crizotinib, but they did not work. Cytarabine was then added as an additional chemotherapy drug for him, and the lesions in the brain and lungs were shrunk by combining treatment of crizotinib, dexamethasone, vincristine, and cytarabine according to the RECIST (esponse Evaluation Criteria In Solid Tumours).

CONCLUSIONS

Additional adjuvant chemotherapy drugs are needed when ALK-inhibitor treatment is ineffective.

Case Report: Rare Systemic and Aggressive ALK-Positive Histiocytosis With Recurrent Pancreatitis Treating by Alectinib

ALK-positive histiocytosis (APH) is a rare and recently described, solitary or generalized, histiocytic proliferative disorder with a characteristic gene translocation involving the fusion of the ALK gene at chromosome 2p23. To date, only 25 cases of APH have been reported. The patient presented with multiple nodules in the lung, liver, gallbladder, pancreas, kidney, and skin rashes, along with recurrent pancreatitis and cholecystitis. The histiocytes from the lesion were positive for CD68 and ALK and negative for S100 and CD1α. A reduced dose of the ALK inhibitor alectinib was administered rather than the standard dose of alectinib or chemotherapy because of recurrent pancreatitis, which has not been previously reported in APH cases. After 18 months of follow-up, the patient was maintained on alectinib, and a partial response (PR) was achieved.

Case Report: ALK-Positive Histiocytosis With KIF5B-ALK Fusion in Cerebrum-Disseminated Lesions in a Child

Background

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare type of histiocytosis that could affect multiple systems in children and adults. 10 cases of ALK-positive histiocytosis invading the central nervous system (CNS) have been reported. Herein, we report a case of ALK-positive histiocytosis invading the central nervous system and lungs and the details of follow-up of tumor dynamic changes during treatment.

Case Presentation

An 18-month-old boy was underweight and had slow growth of almost 3 months duration. The child could not stand and walk independently, and his language and intelligence development occurred later than those of his peers. Cranial magnetic resonance imaging revealed a giant suprasellar lesion with isosignal, measuring approximately 5.1× 3.6× 4.0 cm on T1-weighted imaging, with an obvious mass effect. Nodular, slightly low-signal shadows were also observed in the left temporal pole and left hippocampus, measuring approximately 1.0 cm × 0.7 cm× 0.5 cm and 0.9 cm× 0.8 cm × 0.5 cm on T1-weighted, respectively. The child underwent partial resection of the suprasellar lesion, and a diagnosis of ALK-positive histiocytosis was made histologically. Subsequently, the patient received chemotherapy (CHOP regimen) and anti-ALK therapy (crizotinib). The lesions were gradually shrinking without dissemination and the changes of intracranial and lung lesions were monitored with imaging during therapy. Unfortunately, the child died 8 months after the first surgery because of worsening intracranial infection.

Conclusion

ALK-positive histiocytosis may involve the central nervous system and disseminate intracranially. ALK-positive histiocytosis should be considered for the differential diagnosis of suprasellar lesions.

Distinct Clinicopathologic Features and Possible Pathogenesis of Localized ALK-positive Histiocytosis of the Breast

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare emerging entity characterized by systemic or localized proliferation of histiocytes harboring ALK rearrangements. Breasts are reportedly affected by ALK-positive histiocytosis. Here, we evaluated 2 localized cases of breast ALK-positive histiocytosis through a comprehensive clinicopathologic, molecular, and genomic analysis to further delineate this entity and better understand its pathogenesis. The cases involved 2 undiagnosed ALK-positive spindle-cell breast lesions. Both cases were Asian women aged 30s to 40s who underwent excisions for asymptomatic breast masses. Macroscopically, both lesions were well-circumscribed, solid masses. Microscopically, both lesions were predominantly composed of fascicles with uniform, bland spindle cells, admixed with epithelioid histiocyte-like cells and lymphoid aggregates. Immunohistochemically, the spindle and epithelioid cells coexpressed ALK and histiocytic markers (eg, CD68, CD163). Genetically, both lesions harbored KIF5B-ALK, confirmed by fluorescence in situ hybridization and polymerase chain reaction-direct sequencing analyses. Combining these results, both cases were successfully diagnosed as ALK-positive histiocytosis. Furthermore, no common or previously annotated somatic alterations were identified by whole-exome sequencing. One case harbored clonal immunoglobulin gene rearrangements according to the polymerase chain reaction-based BIOMED-2 protocol. Therefore, ALK-positive histiocytosis can be accurately diagnosed through a combination of morphologic, immunohistochemical, and molecular analyses. In this entity, breast cases may have distinct clinicopathologic features: Asian women aged 30s to 40s, asymptomatic masses, and predominant spindled morphology. For pathogenesis, ALK rearrangements could be the driver alteration, and a subset of ALK-positive histiocytosis may harbor a lymphoid lineage. These findings can be utilized to improve the diagnosis of ALK-positive histiocytosis and better understand its pathogenesis.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

Local ALK-Positive Histiocytosis With Unusual Morphology and Novel TRIM33-ALK Gene Fusion

ALK-positive histiocytosis was first described in 2008 as a systemic histiocytic disorder involving young infants and neonates. Subsequently, cases of local ALK-positive histiocytosis as well as clinical presentation in adult patients have been increasingly reported in the literature. The current case documented the hitherto largest local ALK-positive histiocytosis lesion involving the mesentery of a 20-year-old female patient, a clinical presentation that has not been previously reported in the medical literature. Of note was the presence of numerous lymphocytes, plasma cells, and eosinophils as well as the formation of lymphoid follicles in the lesion, mimicking an inflammatory myofibroblastic tumor. Other unique histologic aspects of the current case included the nested arrangement of the histiocytes, intravascular extension of the histiocytic proliferation into a large vein, and tumor necrosis. Notably, molecular studies revealed a novel TRIM33 (exon 12)-ALK (exon 20) gene fusion. Therefore, ALK-positive histiocytosis with TRIM33-ALK gene fusion expands the clinical, histologic, and molecular spectrum of local ALK-positive histiocytosis. Since ALK-positive histiocytosis associated with a significant inflammatory component can pose considerable diagnostic challenges, increased awareness of this peculiar variant of ALK-positive histiocytosis is essential to minimize the risk of misdiagnosis.

ALK-rearranged histiocytosis: Report of two cases with involvement of the central nervous system

AIMS

Histiocytoses are a heterogeneous group of localized or disseminated diseases. Clinical presentation and patients' outcome vary greatly, ranging from mild to life-threatening disorders. Rare cases of systemic or localized histiocytosis harboring ALK rearrangement have been reported.

METHODS

Two cases of CNS histiocytosis were thoroughly investigated by implementing multiple molecular tests, i.e. FISH, RT-qPCR, NGS analysis.

RESULTS

In a 10-month old girl (patient #1), MRI showed two left hemispheric lesions and a right fronto-mesial lesion histologically consisting of a moderately cellular infiltrative proliferation, composed by CD68(PGM1)+/CD163+ spindle cells. ALK 5'/3'-imbalance and a KIF5B(exon 24)-ALK(exon 20) fusion were documented by RT-qPCR and NGS analysis, respectively. A subsequent CT scan showed multiple hepatic and pulmonary lesions. The patient was started on chemotherapy (vinblastine) associated to an ALK-inhibitor (Alectinib) with remarkable response. In a 11-year-old girl (patient #2), MRI showed a right frontal 1.5 cm lesion. Neuropathological examination revealed a histiocytic proliferation composed by medium sized CD68(PGM1)+/HLA-DR+ cells, showing moderate ALK1 positivity. ALK rearrangement and a KIF5B(exon 24)-ALK(exon 20) fusion were demonstrated also in this case. Subsequent CT, 18F-FDG-PET and MRI scans showed the presence of a single right femoral lesion, proved to be a fibrous cortical defect.

CONCLUSIONS

In ALK-histiocytoses, CNS involvement may occur as part of a systemic disease or, rarely, as its only primary disease localization, which could remain otherwise asymptomatic. The diagnosis often relies on neuropathological examination of brain biopsy, which may pose a diagnostic challenge due to the variable histopathological features. An integrated histological and molecular approach in such cases is recommended.

ALK-positive Histiocytosis of the Breast: A Clinicopathologic Study Highlighting Spindle Cell Histology

Originally described as a systemic self-limiting disease in infancy, the spectrum of ALK-positive histiocytosis has recently been broadened to include localized diseases in older children and young adults. Despite different manifestations, these tumors share histologic characteristics and a highly recurrent KIF5B-ALK fusion. ALK-positive histiocytosis is poorly characterized in the breast. In this study, we report 3 cases of ALK-positive histiocytosis of the breast. The patients were Asian women, aged 16 to 45 years. Two patients presented with an isolated breast mass, while 1 exhibited multiorgan involvement. The latter patient received ALK inhibitor after surgery, which led to complete remission. Histologically, well-circumscribed tumors displayed fascicular and storiform growth of uniform, nonatypical spindle cells admixed with lymphocytic infiltrates. Fewer conventional epithelioid histiocytes with lobulated or clefted nuclei were observed within the same breast tumors in 2 cases or within a concomitant brain tumor in the third case. Touton-type giant cells were focally present in 2 cases. Immunohistochemically, tumor spindle, and epithelioid cells were diffusely positive for CD163 and ALK in all cases and focally positive for S100 protein in 1 of the cases. CD1a and langerin were negative. Actin-positive myofibroblasts were admixed within the tumor in 2 cases, and their reactive nature was highlighted using double immunostaining. Break-apart fluorescence in situ hybridization assay demonstrated gene rearrangements involving KIF5B and ALK in all the 3 cases. ALK-positive histiocytosis rarely occurs as a spindle cell breast tumor, and should be distinguished from other diseases such as inflammatory myofibroblastic tumors and spindled histiocytic reaction.

ALK-Positive Histiocytosis: A Case Report and Literature Review

ALK positive histiocytosis is a relatively new histiocytic proliferation disease with a characteristic gene translocation involving fusion of the ALK gene with different partners, mostly KIF5B. We report a case of ALK-positive histiocytosis with literature review. A 27-year-old male patient presented mainly with progressive lower limb weakness. Imaging studies showed an intradural extramedullary enhancing lesion at the L3 level. A 1.5 cm mass was excised from the sensory nerve root in the filum terminale at the level of L3. Histologic examination showed infiltration of the nerve by numerous histiocytes with moderate to abundant eosinophilic to clear-foamy and variably-vacuolated cytoplasm with irregular-to-smooth contoured nuclei. The histiocytes were positive for CD68 and ALK1 and negative for S100 and CD1a. KIF5B-ALK fusion was detected by real time-polymerase chain reaction. The patient is asymptomatic nine months after surgical excision. This is the first reported localized case occurring in the nerve root of an adult patient, thus expanding the clinical manifestations of this disease. An integrated histological, immunohistochemical and molecular approach is recommended for diagnosis. We recommend performing ALK1 immunohistochemical stain on all histiocytosis cases to increase awareness and detection of this newly described entity.

ALK-positive histiocytosis associated with chronic lymphocytic leukaemia/small lymphocytic lymphoma: a multitarget response under ibrutinib

ALK-positive histiocytosis is a recently described entity with few reported cases in literature. Herein, we report an unusual case of ALK-positive histiocytosis showing an Erdheim-Chester disease (ECD)-like presentation, occurring in a 37-year-old woman with a 2-year history of chronic lymphocytic leukaemia (CLL). Our CLL patient relapsed 6 months after the end of fludarabine, cyclophosphamide and rituximab frontline therapy and complained of lower limb pains. A bone marrow biopsy was performed and showed concomitant CLL/small lymphocytic lymphoma and ALK-positive histiocytosis with an identical immunoglobulin heavy-chain gene rearrangement in both neoplasms, suggesting clonal relationship. After 4 years under ibrutinib therapy, our patient remains free of both diseases. This report extends the spectrum of composite hematolymphoid neoplasms and shows that ALK rearrangement should be considered in all histiocytosis subtypes. Moreover, both tumours eradication under ibrutinib suggests that BTK inhibitors may also be effective in histiocytic neoplasms.

ALK-Positive Histiocytosis with Peripheral Blood Histiocytes: A Case Report

Histiocytoses are a diverse group of rare, clinically heterogeneous disorders characterised by tissue infiltration of histiocytes, which may result in organ dysfunction and failure. Over 100 different subtypes of histiocytoses have been recognised, including rare cases of ALK-positive histiocytosis. We report a case of histiocytosis in a neonate who presented with refractory thrombocytopenia, anaemia, and intermittent neutropenia. Histiocytes were present in both peripheral blood smears and bone marrow; ALK positivity was demonstrated by immunohistochemistry. Given the scarce reports of this condition, the variable organ involvement, and the different approaches to management in the cases described, we seek to expand the literature by providing a report of our patient whose condition improved without chemotherapy. The presence of histiocytes in peripheral blood smears of patients with this condition has not previously been reported, and it underscores the importance of routine careful evaluation of blood smears.

ALK-positive histiocytosis: an expanded clinicopathologic spectrum and frequent presence of KIF5B-ALK fusion

In 2008, we presented three cases of ALK-positive histiocytosis as a novel systemic histiocytic proliferation of early infancy with hepatosplenomegaly and dramatic hematological disturbances. This series of 10 cases (including the original three cases) describes an expanded clinicopathological spectrum and the molecular findings of this histiocytic proliferation. Six patients had disseminated disease: five presented in early infancy with eventual disease resolution, and the sixth presented at 2 years of age and died of intestinal, bone marrow, and brain involvement. The other four patients had localized disease involving nasal skin, foot, breast, and intracranial cavernous sinus - the first three had no recurrence after surgical resection, while the cavernous sinus lesion showed complete resolution with crizotinib therapy. The lesional histiocytes were very large, with irregularly folded nuclei, fine chromatin, and abundant eosinophilic cytoplasm, sometimes with emperipolesis. There could be an increase in foamy histiocytes and Touton giant cells with time, resembling juvenile xanthogranuloma. Immunostaining showed that the histiocytes were positive for ALK, histiocytic markers (CD68, CD163) and variably S100, while being negative for CD1a, CD207, and BRAF-V600E. Next-generation sequencing-based anchored multiplex PCR (Archer® FusionPlex®) performed in six cases identified KIF5B-ALK gene fusion in five and COL1A2-ALK fusion in one. There was no correlation of gene fusion type with disease localization or dissemination. The clinicopathological spectrum of ALK-positive histiocytosis is broader than originally described, and this entity is characterized by frequent presence of KIF5B-ALK gene fusion. We recommend that every unusual histiocytic proliferative disorder, especially disseminated lesions, be tested for ALK expression because of the potential efficacy of ALK inhibitor therapy in unresectable or disseminated disease.